[WIP] documenting the Releases API

- [ ] the story about how to create/edit releases 
- [ ] how to upload assets
- [ ] Q: can you change the release SHA as part of an update?
- [ ] PR for API refactoring
 - `CreateRelease` -> `Create` in API
 - `EditRelease` -> `Edit` in API
- [ ] PR for extension method to transform a `Release` into a `ReleaseUpdate` object