Splits a language id at its first :.
:
splitLanguageId('diff:django:css') returns ['diff', 'django:css']; splitLanguageId('css') returns ['css', undefined].
splitLanguageId('diff:django:css')
['diff', 'django:css']
splitLanguageId('css')
['css', undefined]
Splits a language id at its first
:.splitLanguageId('diff:django:css')returns['diff', 'django:css'];splitLanguageId('css')returns['css', undefined].