Fix: Migrating from Skypack to esm.sh

[gw31415]

Thanks for the useful plugin.

Issue

I get an error when installing for the first time:

[Package Error] "@octokit/[email protected]" could not be built.

It seems to be due to the use of Skypack. This pr switches to esm.sh from Skypack.

We do't publish to skypack, skypack is pulling from the npm registry. Skypack is no longer maintained, please try esm.sh

Originally posted by @gr2m in https://github.com/octokit/octokit.js/issues/2496#issuecomment-1633602260