v0.3.0

• Add integration test (#275)
• [windows] add show and hide events (#274)
• [linux] clean up state tracking (#273)
• Add missing future return values (#272)
• [linux] implement minimizable & maximizable (#270)
• [linux] fix getTitle() crash when null (#269)
• [linux] fix on_window_show and on_window_hide signatures (#268)