.github: test with Node.js 17
.github: test with Node.js 17

I'd usually like to test with the latest release (currently 17.1.0) and
the oldest supported release (currently 12.20 on this branch).  Since
`*` only matches LTS versions, use `'17'` for latest version.

Signed-off-by: Kevin Locke <ffb4761cba839470133bee36aeb139f58d7dbaa9@kevinlocke.name>

kevinoid/appveyor-status,kevinoid/appveyor-status,kevinoid/appveyor-status