Added missing php extension in require statement

I got this error:
`( ! ) Warning: require_once(D:\webdocuments\cm\vendor\hybridauth\hybridauth\hybridauth\Hybrid/StorageInterface): failed to open stream: No such file or directory in D:\webdocuments\cm\vendor\hybridauth\hybridauth\hybridauth\Hybrid\Storage.php on line 8`