`mailto:` is prepended when converting url to link

[sudo-barun]

Steps for Reproduction

1. Visit https://quilljs.com/playground/form
2. Copy-paste the following URL into the Quill Editor:

   https://example.com/@foo.com
   

3. Select the pasted URL and click the link button in Quill Toolbar

Expected behavior:

The input field should contain the original URL i.e. https://example.com/@foo.com

Actual behavior:

The input field contains the original URL with mailto: prepended i.e. mailto:https://example.com/@foo.com

Version: 2.0.2