Update README.md with contribution information

Julien LepillerThu Apr 18 14:25:39+0200 2019

54b501d

nani/app/fastlane/metadata/android/en-US
namelast commitdate
full_description.txtAdd fastlane for Fdroid descriptions.Thu Apr 18 13:36:56+0200 2019
short_description.txtAdd fastlane for Fdroid descriptions.Thu Apr 18 13:36:56+0200 2019