T475 & T503 update navbar and static pages

[maxturer]

Would close #503 and #475. I combined the issues to avoid further git confusion, hopefully it isn't too large of a PR.
This includes:

• navbar restructuring
• anchor links in the new Share Your Work page
• the updated About page
• updated styling for the Contact form
• moved HTML containers to prepare for the new design (some of these are temporary, but looking at the styling has been a bit painful)
• removal of Share Your Work header button styling & CSS
• mobile header redesign (related to lack of share your work button)

[maxturer]

The biggest decision I made here is the mobile header. Compare if you'd like.
Before:

After:

We can always edit this if we need room for a Log In button in the future.