Add localization contribution information to the desktop repository's readme

Closes #237
2 jobs for master in 5 minutes and 10 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #42727
linux kf5-qt5 qt5.12

00:05:10

17.0%
failed #42728
windows
windows kf5-qt5 qt5.13

 
Name Stage Failure
failed
windows kf5-qt5 qt5.13 Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log