Added initial fastlane structure

[ClockGen]

Continuing from #220.

I added a template fastlane structure, filled out some things I could, however there's still the need to replace screenshots and featureGraphic.png with normal ones, so far I simply added blank images of needed resolution. FeatureGraphic is sort of 'banner' that's displayed on app's page. Full description is also nominal and could be improved.

Some things to consider:

• Changelogs should be named as versionCode of each version, right now I named it '32.txt' as of last stable apk, so for new versions new files with corresponding versionCode should be added.
• If you want to add translations to description, they should be added as separate metadata in their respective folders, right now I only added default 'en_US' locale.
• full_description.txt can be formatted with html tags, however some tags are forbidden (more info in reference links below).

More info and reference about fastlane:
https://f-droid.org/docs/All_About_Descriptions_Graphics_and_Screenshots/#fastlane-structure
https://gitlab.com/-/snippets/1895688

[MikuAuahDark]

I'll merge this once I'm done updating the 12.x branch to use the latest upstream.