Docs: Add Next.js Glossary (#88811)
Add next.js glossary so we can reference concepts in guides without
having to re-explain them. Guides should be succint, like a skill :)
Closes: https://linear.app/vercel/issue/DOC-5574/nextjs-glossary
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Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
