Add guessing specs for TypeScript extensions (#1980)

Author: tancnle

lib/rouge/lexers/typescript.rb

@@ -10,7 +10,7 @@ class Typescript < Javascript
       extend TypescriptCommon
 
       title "TypeScript"
-      desc "TypeScript, a superset of JavaScript"
+      desc "TypeScript, a superset of JavaScript (https://www.typescriptlang.org/)"
 
       tag 'typescript'
       aliases 'ts'

spec/lexers/typescript_spec.rb

@@ -10,6 +10,8 @@
     it 'guesses by filename' do
       assert_guess :filename => 'foo.ts'
       assert_guess :filename => 'foo.d.ts'
+      assert_guess :filename => 'foo.cts'
+      assert_guess :filename => 'foo.mts'
     end
 
     it 'guesses by mimetype' do