add rtd setup instructions

readthedocs_setup.md

@@ -0,0 +1,23 @@
+# readthedocs setup notes
+
+* Settings
+  * Programming Language: `Python`
+* Advanced Settings
+  * Default version: `Stable` (ideally)
+  * Versioning scheme: `Multiple versions without translation`
+  * Build pull requests for this project
+* Integrations
+  * GitHub Incoming Webhook
+* Environment variables
+  * `SPHINX_GITHUB_CHANGELOG_TOKEN`: provide a read-only fine-grained github token (https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens#fine-grained-personal-access-tokens). I have an active one. It'll require renewal at least every 12 months.
+* Automation rules
+  * Stable release rule
+    * Match: `Custom match`
+    * Custom match: a pattern for latest stable release
+    * Version type: `Tag`
+    * Action: `Set version as default`
+  * Dev version release rule
+    * Match: `Custom match`
+    * Custom match: a pattern for a dev release
+    * Version type: `Tag`
+    * Action: `Activate version`