Add YARD documentation to release-toolkit actions

[AliSoftware]

Add YARD documentation to all the methods in release-toolkit, especially the methods on actions and helpers.

Part of this task will likely be tackled in parallel to the code rearrangement / refactoring in #191 – as we plan to write YARD documentation for new code as it is being refactored / rewritten. But this issue will cover more than #191 as we need to also document even code that won't really need to change / be refactored.

• [ ] Helpers
  • [ ] *_version_helper iOS + Android (🚧 WIP)
  • [ ] *_git_helper iOS + Android (🚧 WIP)
  • [ ] Other iOS helpers (🚧 WIP)
  • [ ] Common (non-platform-specific) helpers
• [ ] Actions
  • [ ] Android actions
  • [ ] iOS Actions
  • [ ] Common Actions
  • [ ] Configure Actions