howto_release: add documentation on how to release a new version

hwoto_release.md

@@ -0,0 +1,35 @@
+## How to release a new version on PyPi
+
+1. Ensure a new version number is set in `pyproject.toml`.
+
+2. Create and push a fresh tag:
+   ```
+   git tag -s -a v1.0.2 -m "Release adapting to Indico 3.3.4 and new build system"
+   git push --tags
+   ```
+
+3. Clean up:
+    ```
+    rm -rf venv
+    rm dist/*
+    ```
+4. Create a fresh `venv` and activate it:
+    ```
+    python -m venv venv
+    source venv/bin/activate
+    ```
+
+5. Install the plugin and build tooling inside, and build:
+   ```
+    python -m pip install -e .
+    python -m pip install build
+    python -m build
+    ```
+
+6. Assuming you have `twine` already on your system and have API keys at hand, check and upload the packages:
+    ```
+    twine check dist/*
+    twine upload -r testpypi dist/*
+    twine upload dist/*
+    ```
+7. After the release, bump the version number in `pyproject.toml` to allow for future developments.