Delayed Link Preview

To prevent issues as mentioned in the settings page related to generating link previews there are a few cool ways to handle it. 1. Delay generating link previews by a time specified by the user (even with a default allow for custom delay) 2. Delay generating until it is rendered in the UI (this introduces problems of expiring links) 3. Rules filter with some standard options (like images being rendered in the browser to try and defeat download measures, or .gov websites) and regex (this is easy to *do* but could become a support nightmare depending on the general technical level of the userbase)