Add initial fastlane structures for F-Droid submission

[IzzySoft]

Initial Fastlane metadata for your listing in F-Droid. Please build on this and add e.g. screenshots (preferably without frames, think of those folks on their small smartphone screens – but of course that's your decision). For guidance, feel free to use my Fastlane Cheat Sheet.

[adeekshith]

Thanks for your effort @IzzySoft ! Really appreciate it!

add e.g. screenshots (preferably without frames, think of those folks on their small smartphone screens

Thats a good point. Will include frameless screenshots too and go through your cheat sheet. Thank you!

[IzzySoft]

Thanks for merging!

Will include frameless screenshots too

My repo already has the "frameless versions" (cropped from your full-res screenshots here in the repo). Now that you've merged this, I'll update metadata on my end to pull Fastlane with new versions whenever you adjusted that (done).

Another pointer, for formatting of the full_description.txt: the Fastlane page in my wiki. My repo supports all 3 variants. As pointed out, I'd suggest you use "Markdown lite" (which is also what I submitted with this PR), as that works fine with F-Droid (and except for links and HTML parts, Play Store) as well.