Reframe as multi-editor snippet collection

[alDuncanson]

Companion to the repo-metadata updates (description + topics, already applied):

• README intro: "gives you a shorthand snippet for every hook in the React docs — in VS Code, VSCodium, and Neovim" instead of "is a VS Code extension with…"
• Manifest description: "A snippet for every React hook" — the platform-neutral tagline (feeds both the VS Marketplace and, eventually, Open VSX)
• Keywords: es6 → react-hooks

Marketplace-facing copy stays snippet-focused; the multi-editor story lives where multi-editor users look.