Display instance/community rules in report sheet

[Sjmarf]

We could bullet-point the instance and community rules and add buttons next to each to auto-fill the "reason" box. We could also have this for the post removal sheet.

To do this, we'd need to traverse the markdown tree for the instance sidebar and attempt to find a rules list. It should be pretty easy to identify in most cases. For some cases, however, this is impossible - lemmy.world, for example, has their rules list on a webpage rather than in the sidebar. The only way to cover that case would be to hardcode the rules list on a server that we operate, and the client could query the server to get the list of rules. That's a lot of work to implement, though.

If we wanted to get really fancy, we might be able to compare the content of the target post/comment with the rules list and use on-device ML to find a matching rule, then display a suggestion for that rule more prominently.