initial fastlane structures from IzzyOnDroid

[IzzySoft]

this PR provides you with a "fastlane starter package" – to give it into your hands to define how your app is presented, and make it easy to keep descriptions & graphics in sync with your development. Some notes to sum them up in a place easy to find for you:

• the IzzyOnDroid Fastlane Documentation can guide you with maintaining the structures here
• take special care for limits, e.g. per-release changelogs can have max 500 chars, full_description.txt max 4,000 chars, graphics must have specific aspect ratios etc.
• you can have "bigger graphics" here; the IoD updater takes care to resize/optimize them as needed
• for the full_description.txt here I've used HTML compressed into a single line, to prevent the fdroid software converting each line break to a <br>. The tags used for this are supported by F-Droid.org as well, and to my knowledge even by PlayStore.
• whenever you add a new "type" of metadata that has not been there before (e.g. the first changelog, a featureGraphic if it wasn't yet present), please let us know so we can check and enable it.
• Details on all this in the linked documentation.
• Once merged, your changes will be synced whenever a new release is pulled in here – to make sure it stays up-to-date with the app itself.
• Should you have questions, be welcome to ask 😉

And now: Enjoy!

PS: you're also welcome to pick a badge linking to https://apt.izzysoft.de/packages/moe.nb4a, where NekoBox is available since 2023-03-15. We ship the APK built and signed by you (taken from your Github releases), which can be easily verified (signature check) – and make it available via our repo, so it can be easily installed and kept updated using an F-Droid client of your choice. Some download stats for you:

[IzzySoft]

@arm64v8a any chance to get this merged? As we need to move on with our repo reorg at IzzyOnDroid, it would help us a lot. Thanks in advance!

[IzzySoft]

We're now about to finalize our repo reorg, and thus would very much appreciate having this PR merged – so description & graphics can be kept in sync 🙏 For some motivation, these are the stats of installs/updates for your app at IzzyOnDroid, @arm64v8a

About 1k each month – that should be worth being properly supported, right? 😉

[IzzySoft]

I feel a bit ignored here 🙈 Is there any statement at least, @arm64v8a? I cannot even tell if you missed this PR entirely.