Move PlayStore description to Fastlane

The [/docs/marketing/localized_description](https://github.com/ankidroid/Anki-Android/tree/main/docs/marketing/localized_description) contains translations of the app description that is used in the PlayStore.

But this doesn't work for the F-Droid and it remains untranslated https://f-droid.org/de/packages/com.ichi2.anki/
The F-Droid expects that translations will be located in the [/fastlane/metadata/android](https://github.com/ankidroid/Anki-Android/tree/main/fastlane/metadata/android) folder. During a new app release it will take automatically this descriptions.
So could you please move the the files under correct location? Or will you accept a PR for this.

The Crowdin has the `/14-marketdescription.txt` so it also should be moved there.