Support custom protocol links in Plugins

Currently, it looks like only the `http(s)://`, `mailto://` and `tel://` protocols are supported as navigable links from within a plugin.

It would be great to offer support to click into other custom native apps with their own protocol, like `slack://...`, `zoommtg://...`, `notion://...`, etc

Ideally allow the Plugin developer to specify which custom protocols should be allowable from "this" plugin.