You can create new files that use any extension in your cPanel account.

From your client area go to:

Services -> My Services -> click on the green "Active" button -> Login to cPanel/Control Panel

In the top left-hand corner of the account Dashboard, select File Manager.

In the cPanel File Manager, select +File. Complete the on-screen fields, and then select Create New File.

More info: For more help, see the cPanel documentation for File Manager.