initial fastlane structure from IzzyOndroid

As discussed in #33 here comes the "starter package". While usually fastlane lives in `/fastlane/metadata/android`, Ive added it to `/metadata` (the F-Droid internal location) as you already had that directory created in your repo. This works fine as well: F-Droid finds it here automatically, and with my repo I can configure the "entry point" for each app separately. For working on it, be welcome to use my [Fastlane Cheat Sheet](https://gitlab.com/-/snippets/1895688) as reference. You might e.g. wish to replace/update the screenshots, update the "full description" – or add a featureGraphic or even per-release changelogs. If you have any questions, just reach out to me.