Two new built-in layouts: fantasy.yml and economy.yml

Contributes to #97

samples/color_shortcuts.rb

@@ -0,0 +1,6 @@
+require 'squib'
+
+Squib::Deck.new do
+  circle color: 'black', fill_color: 'black'
+  save_png prefix: 'color_shortcuts_'
+end

samples/layouts_builtin.rb

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+require 'squib'
+
+# This sample demonstrates the built-in layouts for Squib.
+# Each card demonstrates a different built-in layout.
+Squib::Deck.new(layout: 'fantasy.yml') do
+  background color: 'white'
+
+  set font: 'Times New Roman,Serif 32'
+  hint text: '#333' # show extents of text boxes to demo the layout
+
+  text str: 'fantasy.yml', layout: :title
+  text str: 'ur',          layout: :upper_right
+  text str: 'art',         layout: :art
+  text str: 'type',        layout: :type
+  text str: 'tr',          layout: :type_right
+  text str: 'description', layout: :description
+  text str: 'lr',          layout: :lower_right
+  text str: 'll',          layout: :lower_left
+  text str: 'credits',     layout: :copy
+
+  rect layout: :safe
+  rect layout: :cut
+  save_png prefix: 'layouts_builtin_fantasy_'
+end
+
+Squib::Deck.new(layout: 'economy.yml') do
+  background color: 'white'
+
+  set font: 'Times New Roman,Serif 32'
+  hint text: '#333' # show extents of text boxes to demo the layout
+
+  text str: 'economy.yml', layout: :title
+  text str: 'art',         layout: :art
+  text str: 'description', layout: :description
+  text str: 'type',        layout: :type
+  text str: 'lr',          layout: :lower_right
+  text str: 'll',          layout: :lower_left
+  text str: 'credits',     layout: :copy
+
+  rect layout: :safe
+  rect layout: :cut
+  save_png prefix: 'layouts_builtin_economy_'
+end
+
+# Stitch together a deck of all the above examples
+Squib::Deck.new(cards: 2) do
+  puts Dir.glob('_output/layouts_builtin_*.png')
+  Dir.glob('_output/layouts_builtin_*.png').each.with_index do |file, i|
+    png file: file, range: i
+  end
+  save_sheet prefix: 'layouts_builtinsheet_'
+end