Stable img processing

Behaviour in a DM with the bot

on first button-press the original pic disappears
a keyboard with buttons pops up
choose an option to get an obfuscated version
press those buttons until happy with the result

Behaviour in groupchats where the bot is added

bot does not detect faces or react to pics
unless any user replies to a pic with the command /pixel
the keyboard with buttons pops up and every user can use them
cancel option removes the buttons (and leaves pic untouched)