Add missing javascript language support

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Change-Id: I56a493db26eb785769cc0cb3058a566f5fc4c9f6

web/element/language.ts

diff --git a/web/element/language.ts b/web/element/language.ts
index 3696b31..ff10478 100644
--- a/web/element/language.ts
+++ b/web/element/language.ts
@@ -211,6 +211,8 @@
     case 'application/x-erb':
     case 'text/x-ruby':
       return StreamLanguage.define(ruby);
+    case 'text/javascript':
+      return javascript();
     case 'text/x-erlang':
       return StreamLanguage.define(erlang);
     case 'text/jsx':