docs: add all current features (#34)

docs/guides/release-notes.md

@@ -1 +1,54 @@
 # Customizing Release Notes
+
+You can customize the generated Release Notes in two ways:
+
+## For a single commit / pull request
+
+This feature is still being worked on. Check out [#5](https://github.com/apricote/releaser-pleaser/issues/5) for the current status.
+
+## For the release
+
+It is possible to add custom **prefix** and **suffix** Markdown-formatted text to the Release Notes.
+
+The release pull request description has text fields where maintainers can add the prefix and suffix. To see these fields, toggle the collapsible section in the description:
+
+![Screenshot of the collapsed section](./release-notes-collapsible.png)
+
+When you edit the description, make sure to put your desired content into the code blocks named `rp-prefix` and `rp-suffix`. Only the content of these blocks is considered.
+
+>     ```rp-prefix
+>     ### Prefix
+>
+>     This will be shown as the Prefix.
+>     ```
+>
+>     ```rp-suffix
+>     ### Suffix
+>
+>     This will be shown as the Suffix.
+>     ```
+
+To match the style of the auto-generated release notes, you should start any headings at level 3 (`### Title`).
+
+Once the description was updated `releaser-pleaser` automatically runs again and adds the prefix and suffix to the Release Notes and to the committed Changelog:
+
+```markdown
+## v1.1.0
+
+### Prefix
+
+This will be shown as the Prefix.
+
+### Features
+
+- Added cool new thing (#1)
+
+### Suffix
+
+This will be shown as the Suffix.
+```
+
+## Related Documentation
+
+- **Reference**
+  - [Pull Request Options](../reference/pr-options.md)