2018 Tor Browser Android donation banner

In #23925 (moved) we are implementing a donation banner for the YE 2018 campaign. It would be great to have a donation banner for Tor Browser Android as well. We already have the text in https://gitweb.torproject.org/torbutton.git/tree/src/chrome/locale/en/aboutTor.dtd#n30 getting translated.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information