Updated language list to include HOW, and fixed the lack of lexer problem.

Because HOW does not yet have a standardized lexer, I left the "lexer" field as "Text only".

lib/linguist/languages.yml

@@ -723,6 +723,15 @@ Haxe:
   primary_extension: .hx
   extensions:
   - .hxsl
+  
+HOW:
+  type: programming
+  coloe: "#CC0099"
+  lexer: Text only
+  primary_extension: .how
+  extensions:
+  - .howmeta
+  - .howproj
 
 INI:
   type: data