Refactor esbuild setup to support watch

[natemoo-re]

Changes

• Version 0.17.0 of esbuild had some breaking changes.
• This updates our astro-scripts package to take advantage of esbuild's new APIs
• Fixes pnpm --filter astro run dev

Testing

Works locally, wasn't before

Docs

No, internal change only

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Latest commit: 2fd28f5

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[bholmesdev]

You better watch out, you better ! cry, you better not error I'm telling you why: esbuild is watching... in deeeeev 🎵