Make doctype case insensetive (#1009)
diff --git a/components/prism-markup.js b/components/prism-markup.js
index 9c074ef..73fe302 100644
--- a/components/prism-markup.js
+++ b/components/prism-markup.js
@@ -1,7 +1,7 @@
Prism.languages.markup = {
'comment': /<!--[\w\W]*?-->/,
'prolog': /<\?[\w\W]+?\?>/,
- 'doctype': /<!DOCTYPE[\w\W]+?>/,
+ 'doctype': /<!DOCTYPE[\w\W]+?>/i,
'cdata': /<!\[CDATA\[[\w\W]*?]]>/i,
'tag': {
pattern: /<\/?(?!\d)[^\s>\/=$<]+(?:\s+[^\s>\/=]+(?:=(?:("|')(?:\\\1|\\?(?!\1)[\w\W])*\1|[^\s'">=]+))?)*\s*\/?>/i,