add fonts methods

Fixes #334

samples/system_font_debug/_list_fonts.rb

@@ -0,0 +1,14 @@
+# require 'squib'
+require_relative '../../lib/squib'
+
+# Per issue #334, sometimes Pango doesn't find the font file you want
+# Pango requires fonts to be installed on the system, but sometimes the
+# font name is not obvious. e.g. "Foo Regular" might be actually named "Foo"
+# Use these methods to debug this problem
+
+# Usually you would just run this method to see what fonts are installed
+# This is commented out to make our test cases
+# Squib.print_system_fonts
+
+Squib.system_fonts.include? 'Open Sans' # checks if we have Open Sans installed
+# Note: does nothing since it's just a check