Add support for Pan Language

As found in repositories related to @quattor, e.g. https://github.com/quattor/template-library-core
The test file provided matches the one I submitted to Pygments.

At some point in the future when the Pygments patches land at GitHub the lexer should be updated from "Text only" to "pan".

lib/linguist/languages.yml

@@ -1500,6 +1500,13 @@ PHP:
   filenames:
   - Phakefile
 
+Pan:
+  type: programming
+  lexer: Text only
+  color: '#cc0000'
+  extensions:
+  - .pan
+
 Parrot:
   type: programming
   color: "#f3ca0a"