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 😉

The second commit adds the IzzyOnDroid badge to the Readme, linking to where NetworkSwitch will show up at around 6 pm UTC (with our next repo sync). Ad the APK was confirmed to be reproducible (congrats 🥳), there's also a shield becoming available within 6h to show the app's latest RB status (see e.g. Reproducible Builds, special client support and more at IzzyOnDroid for some background) if you wish to have it:

[<img src="https://shields.rbtlog.dev/simple/<app_id>" alt="RB Status">](https://shields.rbtlog.dev/com.supernova.networkswitch)

And now: Enjoy!

[IzzySoft]

PS: sneak preview from our staging site:

[aunchagaonkar]

Thanks a lot!. The documentation and notes are super helpful, and I appreciate the clear guidance. Also great to see the IzzyOnDroid badge.

I’ll go through the docs to make sure I maintain things correctly going forward. Thanks again for your support!

[IzzySoft]

Great! And thanks a lot for the swift merge 🤗 activated now at our end, so any changes you make should be taken along whenever a new release is being dragged in to our repo (update checks run daily).

Btw, feel free to switch between HTML and Markdown for the full description (with Markdown, just make sure you use standard Markdown, not Github flavored – but yeah, the docs cover that); these two are covered by the same "import method". Just changing to something else would require adjustments on our end as well.