Enhance texts (only)

Carried out a few enhancements in README.md and config.py
These are solely text changes, going a bit further than the originally addressed "inofficial" --> "unofficial".

The bug I mentioned in the corresponding F-Droid forum thread, that this F-Droid repository always causes the F-Droid client app to "Saving application details", has not been addressed in this PR, as I have no idea what is causing this.

Thanks again for setting up this repository, but while aforementioned bug persists, it is just of little use for me, unfortunately.

HTH & Cheers