Add Dracula theme

More info: https://github.com/zenorocha/dracula-theme

data/themes.yml

@@ -19,6 +19,9 @@
 -
   :name: 'Choco Mint'
   :colors: '#544538,#42362B,#5DB09D,#FFFFFF,#4A3C30,#FFFFFF,#FFFFFF,#5DB09D'
+-
+  :name: 'Dracula'
+  :colors: '#282A36,#44475A,#44475A,#8BE9FD,#6272A4,#FFFFFF,#50FA7B,#FF5555'
 -
   :name: 'DigitalOcean'
   :colors: '#3686BE,#215F8B,#7DB461,#FFFFFF,#2E3234,#FFFFFF,#7DB461,#215F8B'