Allowing :get_matrix in the wrapper

lib/squib/graphics/cairo_context_wrapper.rb

@@ -22,7 +22,7 @@ module Squib
         :show_pango_layout, :rounded_rectangle, :set_line_width, :stroke, :fill,
         :set_source, :scale, :render_rsvg_handle, :circle, :triangle, :line_to,
         :operator=, :show_page, :clip, :transform, :mask, :create_pango_layout,
-        :antialias=, :curve_to
+        :antialias=, :curve_to, :get_matrix
 
       # :nodoc:
       # @api private