Set font antialiasing from global antialiasing

This is a workaround until we get a proper solution in #59

samples/config_text_markup.rb

@@ -1,9 +1,14 @@
 require 'squib'
 
 Squib::Deck.new(config: 'config_text_markup.yml') do
+  background color: :white
   text str: %{"'Yaml ain't markup', he says"},
        x: 10, y: 10, width: 300, height: 200, font: 'Serif 20',
        markup: true, hint: :cyan
+
+  text str: "Notice also the antialiasing method.",
+       x: 320, y: 10, width: 300, height: 200, font: 'Arial Bold 20'
+
   save_png prefix: 'config_text_'
 end
 

samples/config_text_markup.yml

@@ -6,3 +6,4 @@ rdquote: "\u201D"
 em_dash: "\u2014"
 en_dash: "\u2013"
 ellipsis: "\u2026"
+antialias: gray