Attempt to improve site performance

[timothyis]

This pull request changes a few things:

• Enables webpack 5 (many benefits: https://nextjs.org/docs/messages/webpack5)
• Remove preact configuration. This felt like too much additional configuration for a simple site, and we're trying to resolve some performance issues.
• Enables Tailwind JIT for smaller bundles and improved tailwind workflow. (read more on the Tailwind JIT link.)

[vercel]

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