DEVELOPER.md: add instructions on using twine with API tokens

DEVELOPER.md

@@ -28,19 +28,45 @@ Install the following packages:
 $ sudo -H pip3 install setuptools wheel twine
 ```
 
+Starting sometime in 2023, 2FA is required on PyPI. In addition, `twine` no
+longer accepts a password but requires an API token. See
+https://pypi.org/manage/account/token/ on how to generate a token and how to
+configure a `$HOME/.pypirc` file that contains this token. The file will look
+like this:
+
+```
+[distutils]
+  index-servers =
+    pypi
+    bigquery-schema-generator
+
+[pypi]
+  username = __token__
+  password = # insert user-scope or project-scoped token
+
+[schemagenerator]
+  repository = https://upload.pypi.org/legacy/
+  username = __token__
+  password = # insert project-scoped token
+```
+
 ### Steps
 
 1. Increment the version numbers in:
-    * `version.py`
-    * `README.md`
-    * `CHANGELOG.md`
+    - `version.py`
+    - `README.md`
+    - `CHANGELOG.md`
 1. Push all changes to `develop` branch.
 1. Create a GitHub pull request (PR) from `develop` into `master` branch.
 1. Merge the PR into `master`.
 1. Create a new Release in GitHub with the new tag label.
 1. Create the dist using `python3 setup.py sdist`.
-1. Upload to PyPI using `twine upload
-   dist/bigquery-schema-generator-{version}.tar.gz`.
-    * Enter my PyPI login credentials.
-    * If `dist/` becomes too cluttered, we can remove the entire `dist/`
+    - If `dist/` becomes too cluttered, we can remove the entire `dist/`
       directory and run `python3 setup.py sdist` again.
+1. Upload to PyPI
+    - `$ twine upload dist/bigquery-schema-generator-{version}.tar.gz`, or
+    - `$ twine --repository schemagenerator upload
+      dist/bigquery-schema-generator-{version}.tar.gz`
+    - the `--repository PROJECT_NAME` flag is undocumented, seems to map to the
+      `[PROJECT_NAME]` section in the config file
+    - if this flag is omitted, then the `[pypi]` section appears to be used