Add cairo_user_font_face_get_render_color_glyph_func
While testing the meson gtk-doc I noticed I didn't add the cairo_user_font_face_set_render_color_glyph_func
to the documentation. While adding the function to the documentation I noticed I didn't add a getter for cairo_user_font_face_set_render_color_glyph_func
.
This MR fixes both issues.