feat(releasepr): release PRs can be updated

- PR Description
- Read prefix+suffix from PR description and put into changelog
- Keep those overrides on PR description changes
- Add pending level to new PRs

releasepr.md.tpl

@@ -0,0 +1,25 @@
+{{ .Changelog }}
+
+---
+
+## releaser-pleaser Instructions
+{{ if .Overrides }}
+{{- .Overrides -}}
+{{- else }}
+<!-- section-start overrides -->
+> If you want to modify the proposed release, add you overrides here. You can learn more about the options in the docs.
+
+### Prefix
+
+```rp-prefix
+```
+
+### Suffix
+
+```rp-suffix
+```
+
+<!-- section-end overrides -->
+
+{{ end }}
+#### PR by [releaser-pleaser](https://github.com/apricote/releaser-pleaser)