0.5.0

• API: add getters for all properties (fixes #56)
• API: add gtk_layer_is_supported() (fixes #83)
• API: add gtk_layer_is_layer_window(window)
• Docs: add Since: annotations for functions added since the initial release (fixes #82)
• Fix: accept non-1 true boolean values (thanks @alebastr)
• Tests: fix license test for release tarball (fixes #73)
• Tests: test popup with grab (the most likely thing to break on an incompatible GTK version) (fixes #68)