Update README with documentation

Author: jb3

README.md

@@ -6,4 +6,33 @@ functionality of [`python-discord/bot`](https://github.com/python-discord/bot).
 Built images contain a folder `/snekbin/` which contains the built Python
 interpreter (with a binary at `/snekbin/bin/python`).
 
+## Adding new versions
 
+To add new versions to the build matrix, edit the `versions.toml` file to include
+the desired versions. The GitHub Actions workflow will automatically build and
+push the new versions when changes are merged to the main branch.
+
+Additionally, new patch versions are automatically built as part of the cron job
+that runs daily. As long as pyenv is updated upstream with the new patch versions,
+they will be picked up and built without any manual intervention.
+
+### Version Suffixes
+
+Some Python versions have suffixes, these are specified as follows:
+
+| Suffix | Meaning                               |
+| ------ | ------------------------------------- |
+| `j`    | JIT enabled build (e.g., `3.11.0j`)   |
+| `t`    | Free-threaded build (e.g., `3.11.0t`) |
+
+## GitHub Actions
+
+A manual build can be triggered by going to the "Actions" tab and selecting the
+"Build Python Interpreters" workflow. From there, click the "Run workflow" button.
+
+## Built Images
+
+Built images are pushed to the GitHub Container Registry at
+[`ghcr.io/python-discord/python-builds`](ghcr.io/python-discord/python-builds). The
+images are tagged with the Python version they contain, e.g., `3.10.8` as well as the
+short tag, e.g., `3.10`.