General UX improvements

[tjhorner]

Right now the UX is kind of bad. Once installed, users are not really sure what to do. So, in order to make installation and setup as easy as possible, I'd like to add an onboarding:

• [ ] Introduction and explanation
• [ ] Guided config setup (e.g. ArchiveBox URL; could probably do something slick here by looking in the history for ArchiveBox URL routes like /add/ and /admin/core/ then suggesting that domain)
• [ ] Guided domain setup (explaining how adding domains and regexes works)
• [ ] (Maybe) option to import a default allowlist/blocklist? Need to see what would be good to add here.

I'd also like to make the domain list UI a bit easier to understand. I'm not entirely sure what it would look like, but right now it looks ugly and cluttered. I'll make some mockups Eventually™️