Migration to github actions and cleanup

[TheMcMurder]

• Change default branch to main
• Update branch protection settings
• Replace yarn with pnpm
• Remove travis.yml
• Remove travis from readme
• Copy GitHub folder, including workflows and funding
• Upgrade husky to v5
• Remove esm-bundle-scripts in favor of independent installations

[TheMcMurder]

So I went down a rabbit hole on this one.

• Turns out there was a breaking change in @rollup/[email protected] that made it so this wouldn't work anymore. For more details on this change check out this PR
• esm-bundle-scripts gave us @rollup/[email protected] so it worked in yarn/npm through dependency flattenting but in pnpm it failed unless I pinned to that version of @rollup/pulgin-commonjs.
• I didn't want to be stuck on an old version of @rollup/plugin-commonjs so I created a src/... file to re-export the modules.
• I didn't want to have to test every single export manually so I wrote some tests that iterate over CJS methods and will fail if something is missing in ESM bundle. This should catch any future API changes automatically.

[joeldenning]

lgtm