[Enhance]: Allow vite-plugin-favicon to save the HTML to a file

[khalwat]

In order to use vite-plugin-favicon with backends like Laravel, Ruby on Rails, etc., if the inject setting is off, it should write the HTML result from favicons out to a file.

Implemented via PR: #2

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.