feature: Add a sponsors page

[chasenstark]

PR Checklist

• [x] Addresses an existing open issue: fixes #006
• [x] That issue was marked as status: accepting prs
• [x] Steps in CONTRIBUTING.md were taken

Overview

Adds a sponsors page to list both of our current sponsors. And a little shout out to sponsor us.

[chasenstark]

@JoshuaKGoldberg I've thoroughly licked this cookie, so it's about time I ate it 🍪. My apologies for the serious delay on this. Mind taking a look?

[chasenstark]

I should note that this runs directly into issue #2.

[tjwds]

LGTM, thanks!