Use coincident if crossOriginIsolated, comlink otherwise

[jtpio]

Similar to jupyterlite/pyodide-kernel#126

jupyterlite-xeus should use coincident if crossOriginIsolated, comlink otherwise, to fix the issue noticed in jupyterlite/jupyterlite#1424.

As a follow-up to #87

[jtpio]

Of note, coincident v2 was just released: https://github.com/WebReflection/coincident/releases/tag/v2.0.0

One of the changes is:

the "maybe available" SharedArrayBuffer issue has been fully solved via sabayon which guarantee functionality with or without special headers enabled and it allows people to provide their Service Worker as long as they add sabayon features

So maybe updating to the new version will remove the need for comlink (to be confirmed).

[martinRenou]

it allows people to provide their Service Worker

This is a red flag for me though. Regular async postMessage (what comlink does) should be enough.