message: add support button
diff: <!--- Github page main file --->
  -Gittyup is a graphical Git client designed to help you understand and manage your source code history.
  +Gittyup is a graphical Git client designed to help you understand and manage your source code history. Gittyup is an open source software developed by voluntiers, if you like the application please support us [![Donate Liberapay](https://liberapay.com/assets/widgets/donate.svg)](https://liberapay.com/Gittyup/donate)
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  The release version is available for
  