Example using coi: thanks @jraymakers & @dengkunli

[carlopi]

There were two independent PRs on enabling examples using COI:

• esbuild-browser example using coi #1424, that was missing a bit of the pthread syncronization dance
• Add OPFS support #1490, that is centered around OPFS, and this seems an orthogonal feature

I took the liberty of merging them into this PR.

Thank you both for the contribution.

I will add enabling shell as a follow up.

[Mytherin]

Thanks