Add conferences section to /schedule

[vcarl]

We'd like to offer a better "community partner" option for upcoming conferences, and I think a heading section on our schedule page would be a great place to do so. It might make sense to do this as frontmatter so we can render it as a horizontal list of icons + blurbs, rather than a vertical paragraph content like the rest of the schedule.

[vcarl]

I think this would be redundant to the conferences list on the react.dev site, so gonna close this as wontfix