Fastlane: improvements to full description

Currently, your full description is rather just a bullet point list – and doesn't render as Markdown (which e.g. IzzyOnDroid supports). To compare with what we currently have set up here:

with how it would look had we taken your fulldesc, as F-Droid does:

I don't know how you maintain your fastlane locales, so I especially didn't want to go for the length of adjusting that in all of them, just to have a related PR rejected as it doesn't fit your workflow (no offense meant, but it might be trouble if you use some translation service, for example, as it then would require extra work at your end to get that synced).

If you'd be interested, I could send you the full description as it's set up here. Let me know if you use a translation service, so I can reformat it in a way friendly to that – in a format rendering fine as "plain text" (for F-Droid) as well as in Markdown (for IzzyOnDroid). I gladly provide that if it's welcome.

If not, we'd need to remove our local modifications, and switch to the same plain-text formatting F-Droid uses – as otherwise we'd run out of sync with your changes here.

Thanks in advance for taking the time to look into this – and we look forward to your response then.

No files or tests are named. Start by reviewing the Fastlane locale workflow and the two referenced description renderings, then determine whether Markdown formatting or F-Droid-compatible plain text is wanted. Done means the chosen format is agreed and the affected localized full descriptions are synchronized.

Written by the indexing model from the issue text.