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 to link to https://apt.izzysoft.de/packages/org.matrix.chromext e.g. from your Readme – or use this nice shield showing the last known Reproducible Builds status of your app (see e.g. Reproducible Builds, special client support and more at IzzyOnDroid for some background on this):

[<img src="https://shields.rbtlog.dev/simple/org.matrix.chromext" alt="RB Status">](https://shields.rbtlog.dev/org.matrix.chromext)

[IzzySoft]

@JingMatrix 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]

As we're about to finalize our current repo reorg, we'd very much appreciate having this PR merged, @JingMatrix – so description & graphics can be kept in sync. In the hope to give some motivation, here are the monthly installs/updates for ChromeXt at IzzyOnDroid:

[JingMatrix]

Please update the full_description part. Current one is outdated and didn't explain anything about DevTools.

You can send the README to AI for generating a short description.

[IzzySoft]

We don't use AI here. But OK, let me see if I can bring the fulldesc up-to-date (and yeah, I waited much too long with upstreaming those metadata, apologies!).

[IzzySoft]

OK, done (cannot take in the entire Readme, as fulldesc is limited to 4.000 chars – and supposed to give an overview; for full details, we link here anyway). You can of course always update or add, you know best what should be in there (we cannot keep up doing that for 1.3k apps we currently ship with our repo at IzzyOnDroid). Your changes would then be synchronized automatically whenever a new release is being pulled in.

[IzzySoft]

Any chance to get this merged, @JingMatrix – so we can move on with our current repo reorg at IzzyOnDroid? 🙏