Add release steps

Author: anoadragon453

README.md

@@ -137,4 +137,8 @@ Before submitting a PR, make sure to lint your code:
 
 ```
 ./scripts-dev/lint.sh
-```
+```
+
+### Creating a new release
+
+See [RELEASING.md](RELEASING.md).

RELEASING.md

@@ -0,0 +1,45 @@
+# Releasing `mscbot-python`
+
+To make a new release of `mscbot-python`, perform the following.
+
+1. Determine the new version number. This project follows [semantic versioning](https://semver.org/). Store the release version in an environment variable called `RELEASE_VERSION`.
+
+    ```
+    export RELEASE_VERSION=X.Y.Z
+    ```
+
+    **Note:** Do not include a `v` before the version number.
+
+1. Update `setup.py` with the new version number:
+
+    ```
+    sed -i "s/version=\"[0-9]\+\.[0-9]\+\.[0-9]\+\"/version=\"${RELEASE_VERSION}\"/" setup.py
+    ```
+
+1. Stage, commit and push the changes:
+
+    ```
+    git add setup.py
+    git commit -m "$RELEASE_VERSION"
+    ```
+
+1. Create a new git tag:
+
+    ```
+    git tag $RELEASE_VERSION -m "$RELEASE_VERSION"
+    ```
+
+1. Push the tag to the repository:
+
+    ```
+    git push origin $RELEASE_VERSION
+    ```
+
+    **Note:** A docker image will be automatically created and published when
+    the tag is uploaded.
+
+1. [Create a new release](https://github.com/matrix-org/mscbot-python/releases/new)
+    on GitHub.
+    Select the tag that was just created and click "Generate release notes".
+
+1. Press "Publish release", and you're done! 🍾