Add FE tests w/ Robot Framework

After submitting GH-37 as a potential fix for GH-35, I wondered if there was a
way to add FE tests that would detect that sort of issue. I found that [Robot
Framework] is a popular tool for this, and it has a [SeleniumLibrary] that can
be used to interact with web pages. This commit adds a simple test case that
opens a browser, inputs text into the `st_keyup` input field, and waits for the
page to contain some expected text. The test case is run by a shell script that
uses the `robot` command to run the test case.  The test case is run by a shell
script that uses the `robot` command to run the test case.

This test fails with the code on `main` when using Streamlit 1.32.2, because of
GH-35:

```
(.venv)
abramowi at Marcs-MBP-3 in ~/Code/OpenSource/streamlit-keyup (fe-tests-robot-framework)
$ pip freeze | grep '^streamlit'
streamlit==1.32.2

(.venv)
abramowi at Marcs-MBP-3 in ~/Code/OpenSource/streamlit-keyup (fe-tests-robot-framework)
$ ./run-robot-tests
==============================================================================
Robot
==============================================================================
Robot.Test Cases
==============================================================================
Interact with st_keyup                                                | FAIL |
Element 'css:iframe[title="st_keyup.st_keyup"]' not visible after 5 seconds.
------------------------------------------------------------------------------
Robot.Test Cases                                                      | FAIL |
1 test, 0 passed, 1 failed
==============================================================================
Robot                                                                 | FAIL |
1 test, 0 passed, 1 failed
==============================================================================
Output:  /Users/abramowi/Code/OpenSource/streamlit-keyup/tests/robot/output/output.xml
Log:     /Users/abramowi/Code/OpenSource/streamlit-keyup/tests/robot/output/log.html
Report:  /Users/abramowi/Code/OpenSource/streamlit-keyup/tests/robot/output/report.html
```

But it passes with the code in GH-37:

```
(.venv)
abramowi at Marcs-MBP-3 in ~/Code/OpenSource/streamlit-keyup (gh-35-not-rendering-with-streamlit-1.32.2●)
$ git branch
  fe-tests-robot-framework
* gh-35-not-rendering-with-streamlit-1.32.2
  main

(.venv)
abramowi at Marcs-MBP-3 in ~/Code/OpenSource/streamlit-keyup (gh-35-not-rendering-with-streamlit-1.32.2●)
$ git checkout -b gh-35-not-rendering-with-streamlit-1.32.2-with-fe-tests-robot-framework
Switched to a new branch 'gh-35-not-rendering-with-streamlit-1.32.2-with-fe-tests-robot-framework'

(.venv)
abramowi at Marcs-MBP-3 in ~/Code/OpenSource/streamlit-keyup (gh-35-not-rendering-with-streamlit-1.32.2-with-fe-tests-robot-framework●)
$ git merge fe-tests-robot-framework
Merge made by the 'ort' strategy.
 .gitignore                               |  5 ++++-
 run-robot-tests                          |  3 +++
 tests/robot/resources/app_keywords.robot | 16 ++++++++++++++++
 tests/robot/test_cases.robot             | 16 ++++++++++++++++
 4 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100755 run-robot-tests
 create mode 100644 tests/robot/resources/app_keywords.robot
 create mode 100644 tests/robot/test_cases.robot

(.venv)
abramowi at Marcs-MBP-3 in ~/Code/OpenSource/streamlit-keyup (gh-35-not-rendering-with-streamlit-1.32.2-with-fe-tests-robot-framework)
$ ./run-robot-tests
==============================================================================
Robot
==============================================================================
Robot.Test Cases
==============================================================================
Interact with st_keyup                                                | PASS |
------------------------------------------------------------------------------
Robot.Test Cases                                                      | PASS |
1 test, 1 passed, 0 failed
==============================================================================
Robot                                                                 | PASS |
1 test, 1 passed, 0 failed
==============================================================================
Output:  /Users/abramowi/Code/OpenSource/streamlit-keyup/tests/robot/output/output.xml
Log:     /Users/abramowi/Code/OpenSource/streamlit-keyup/tests/robot/output/log.html
Report:  /Users/abramowi/Code/OpenSource/streamlit-keyup/tests/robot/output/report.html
```

[Robot Framework]: https://robotframework.org/
[SeleniumLibrary]: https://robotframework.org/SeleniumLibrary/SeleniumLibrary.html

.gitignore

@@ -32,6 +32,9 @@ latest_logs
 archived_logs
 current-screenshot.png
 
+# Robot framework FE tests
+tests/robot/output/
+
 ########################################################################
 # OSX - https://github.com/github/gitignore/blob/master/Global/macOS.gitignore
 ########################################################################
@@ -75,4 +78,4 @@ package-lock.json
 .direnv/
 .envrc
 
-.streamlit/
+.streamlit/

run-robot-tests

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+robot --outputdir=tests/robot/output --variable=app_url:http://localhost:8501 tests/robot/

tests/robot/resources/app_keywords.robot

@@ -0,0 +1,16 @@
+*** Settings ***
+
+Library             SeleniumLibrary
+
+*** Variables ***
+
+${st_keyup_iframe_locator}   css:iframe[title="st_keyup.st_keyup"]
+
+*** Keywords ***
+
+Input text into st_keyup
+    [Arguments]                         ${text}
+    Wait until element is visible       ${st_keyup_iframe_locator}
+    Select frame                        ${st_keyup_iframe_locator}
+    Input text                          css:input[type="text"]      ${text}
+    Unselect frame

tests/robot/test_cases.robot

@@ -0,0 +1,16 @@
+*** Settings ***
+
+Resource   resources/app_keywords.robot
+
+*** Variables ***
+
+${app_url}                   http://localhost:8501
+
+*** Test Cases ***
+
+Interact with st_keyup
+    Open browser                       ${app_url}    Chrome
+    Input text into st_keyup           adjunta
+    Wait until page contains           URB San Joaquin
+    Wait until page contains           Jard De Adjuntas
+    Wait until page contains           Colinas Del Gigante