Change README.txt to README.md and update according to "README.md template"

The patch works fine. Moving it to RTBC

Since the last reviewer do not pay much attention to details, it would be better somebody else review the MR.

Thanks for reverting these @apaderno. Please see also my comment in #3374414-2: Disturbing behavior by Specbee employee → for another Specbee employee ( nupur-badola → ) with same behavior.