Update to 2.7.7
    
    - Translation updates from Weblate for es, de, pl, he, fr, uk, tr, nl
    - Generate README.html and README from README.md
    - A thorough upgrade to README.md
      Resolves: https://github.com/mike-fabian/ibus-typing-booster/pull/74
    - Set button label of google application credentials button correctly
      Resolves: rhbz#1793460
    - Make si-wijesekera the default input method for si_LK.UTF-8 locale
    - Add another test case for libvoikko spellchecking together with
      en_GB spellchecking