v0.2.9

• [windows] Fix set maximizable throwing an error (#267)
• [linux] clean up unused includes (#260)
• [linux] fix window geometry hints (#257)
• [linux] pass the plugin instance around as user data (#256)
• [linux] fix getOpacity() (#255)
• [Linux] use g_strcmp0() (#254)
• [Linux] remove misleading C++-style default values (#253)
• [Linux] implement setBrightness() (#252)
• [Linux] fix frameless window & background color (#250)
• [Linux] make setTitleBarStyle() GTK/HDY/CSD/SSD compatible (#249)