Support For User-Customizable Links

[kj800x]

I think nu add or nu custom could take the user to an extension page where they could customize some links.

[kj800x]

For now, I don't think this is in scope for the extension. Ideally, if it's a Northeastern link, the user can make a suggestion on this GitHub and we can quickly add it and publish an update. If it's not a Northeastern link, then this extension is probably not the best place to manage it.

[kj800x]

Realizing that there are some nu-specific sites which are probably only useful for certain users (such as the CS4500 website, which affects specific users and depends on the year and the section). Definitely, we should suggest that users consider whether it would be useful for a wider audience and to direct them to post in here if that's the case.

We could use localstorage for the website and probably some storage api for the extension. I wonder if we could sync localstorage between multiple computers for the users and if we could sync the website and the extension storage.

Probably requires a page to manage user-links. Support adding user links by URL query params (with a confirm dialog to add the link).