Add 'data' field to svg method for loading XML directly

Implements #65

samples/embed_text.rb

@@ -61,7 +61,7 @@ Squib::Deck.new do
   text(str: embed_text, font: 'Sans 21',
        x: 400, y: 320, width: 180, height: 300,
        align: :center, ellipsize: false, justify: false, hint: :magenta) do |embed|
-    embed.svg key: ':tool:',   width: 28, height: 28, file: 'spanner.svg'
+    embed.svg key: ':tool:',   width: 28, height: 28, data: File.read('spanner.svg')
     embed.svg key: ':health:', width: 28, height: 28, file: 'glass-heart.svg'
     embed.png key: ':purse:',  width: 28, height: 28, file: 'shiny-purse.png'
   end

samples/load_images.rb

@@ -17,6 +17,20 @@ Squib::Deck.new(width: 825, height: 1125, cards: 1) do
   # Squib prepends a #-sign if one is not specified
   svg file: 'spanner.svg', id: 'backdrop', x: 50, y: 450, width: 125, height: 125
 
+  # We can also load SVGs as a string of XML
+  svg data: File.read('spanner.svg'), x: 50, y: 600, width: 75, height: 75
+
+  # The svg data field works nicely with modifying the SVG XML on-the-fly.
+  # To run this one, do `gem install game_icons` and uncomment the following
+  #
+  # require 'game_icons'
+  # svg data: GameIcons.get('angler-fish').recolor(fg: '#ccc', bg: '#333').string,
+  #     x: 150, y: 600, width: 75, height: 75
+  #
+  # More examples at https://github.com/andymeneely/game_icons
+  # (or `gem install game_icons`) to get & manipulate art from game-icons.net
+  # Nokogiri (already included in Squib) is also great for XML manipulation.
+
   # WARNING! If you choose to use the SVG ID, the x-y coordinates are still
   # relative to the SVG page. See this example in an SVG editor
   svg file: 'offset.svg', id: 'thing',  x: 0, y: 0, width: 600, height: 600