CI: Introduce tests for JS-peer

[maschad]

It would be good to have a basic ping test akin to the one in js-libp2p ping module to ensure that breaking changes are caught at runtime.

[2color]

Do the ping module tests in js-libp2p run in the browser?

[maschad]

Yup, we use aegir to run them

Aegir uses https://github.com/microsoft/playwright under the hood to run the browser tests.

I've also had a good experience using vitest's browser mode as well so that would be my recommendation.