Adds a new nav item "Summer School" to the top site menu
Temporary: I'll remove it this year after the summer school
Bolded to draw attention
Adds an entry for this year's summer school to the Meetings page
Fixes a bug where "Blog" in the nav menu wasn't switching to black font when you're on the page
Questions for Julie:
We should make a blog post announcing the summer school next, right?
The Meetings page is starting to feel long and cluttered. Do you agree? I had an idea to move everything underneath the calendar into subpages: "Community Meetings", "Conference Sessions", "Summer Schools". Want me to?
This PR does three things:
Questions for Julie: