feat: Add a generic "Connector / Plugin not found" page
We should have a generic Connector / Plugin not found page that directs users to submit a request and/or points them to the SDK and community for how to create it. Particulary in the case of when a github repo disappears (like exact target) and we need to point the users to something. See #753 for some more discussion.
@tayloramurphy Is this in addition to a normal 404 page? Would adding particular language to the 404 page work just as well?
@alexmarple I'm thinking that for pages under certain paths we may have a more focused 404 page, but I'm not 100% sure yet. Maybe it'd be better to just have placeholders rather than a 404 page 🤔