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