Add [event].tsx page #153

This is the [event].tsx page that displays a single event, with a couple of sample events in content/events for testing purposes.

Closes #114

Just 1 nit-pick, LGTM otherwise!

Make sure to delete the markdown files before merging!!

     await Promise.all(
       years.map(async (year) => {
         const termsInYear = await getEventTermsByYear(year);
         return termsInYear.map((term) => ({ year, term }));