Proposal of versioning numbering method change for the next release

[misl6]

• kivy-ios releases currently use semantic versioning (last release was 1.3.0). (MAJOR.MINOR.PATCH)
• Like python-for-android, many changes in kivy-ios are driven by XCode / iOS / macOS updates.
• More often we're encouraging users on our support channels to use the latest changes available on the master branch in order to avoid issues they're encountering with the released version of kivy-ios.
• semantic versioning doesn't allow us to release a minor release if it only contains patches.
• Managing (and releasing) multiple minor versions at the same time, in order to contain the needed patches is hard.

Considering these points, the proposal is to change the versioning numbering method change for the next release.

The most obvious idea is to use the calendar versioning <https://calver.org/> ( YYYY.0M.DD ), as it's the same versioning method that python-for-android started using 3 years ago, for a similar reason.

[AndreMiras]

I have nothing against it 👍

[misl6]

Fixed via #734