Guide post-MVP

We implemented guides in #2600. Now let's make improvements. Using this issue to compile all the ideas.

- [ ] Minimum required section behavior
- [ ] Download checklist
- [ ] Download application documents
- [ ] Checklists
- [ ] Bullet style with checkbox
- [ ] Need to not have to use code to create line breaks
- [ ] Documents section behavior
- [ ] Lists all the documents that are linked to within the guide. Note that this includes CoA documents that are pointed to within pages, but not documents that are linked to that are not CoA.
- [ ] Headings correspond to the sections in which the documents originated
- [ ] ❓Clicking on a document name opens the file in a new tab
- [ ] ❓(For MVP?? This could be curated by a content editor, so instead include this in style guide/content governance documentation) In the case of duplicate documents (found on one or more pages), the preferred behavior would be to show the document where its first referenced within the guide. We want to avoid duplicating links because that's confusing to users. For example, if an application doc is linked to in Section 1 and then again on a different page in Section 3, then only show that document in Section 1 of Documents, but not again in Section 3.