Proposal: Kit, doc-kit's mascot, and a tagline for the site #1197

Hey folks 👋

On #1192 we agreed the branding needs its own discussion, so here's a proposal for it. The PR uses all of this for now, and I'm happy to swap any of it for whatever we land on here.

Kit

A cat called Kit, after doc-kit. It's a flat head, so it works as a mark from a 16px favicon up to the home page's hero, in both color schemes, and it has a couple of poses for the spots where the site can be a bit playful: asleep on the 404 page, and peeking over the home page's last section.

On the PR the drawings live in www/theme/components/Brand.jsx and www/public/.

Tagline

The home page's headline is a placeholder for now, "The docs toolkit for APIs." A few other ideas:

• The docs toolkit for APIs.
• API docs from plain Markdown.
• Write it once, get every format.
• The toolkit behind the Node.js API docs.

Colors

The site sticks to the neutral greys doc-kit's default theme already uses, no green, so it doesn't read as a Node.js page out of the box.

What do y'all think?

cc @avivkeller