Add some guidance about landing pages

[nonprofittechy]

• Important to highlight the information people need before they start
• share the link to the landing page if possible, not the direct interview link
• user's often don't read it, so focus on just-in-time help
• SEO: short description and a meta description, common language people use to refer to the form rather than just what's on the page.

[samglover]

#470 and #463 are separate issues, but there will be some overlap and we'll want to avoid duplicating content.

[samglover]

Added an SEO page in #511

[samglover]

I don't think Copilot addressed this very well. Most of the issue was already solved in #511. About half of Copilot's work duplicates the existing SEO guidance (poorly). The first half of the page addresses the remainder of this issue, but not very well. It's mostly generic and repetitive of other, better documentation we already have.

I suggest reverting #540 and keeping this issue open to be addressed by a human.