feat: add h3 v2 support

[CodeDredd]

Closes #14

Problem

h3 v2 fundamentally changes the response pipeline and breaks this package:

• The send utility is removed, so import { send } from 'h3' fails to load the module under v2.
• The onBeforeResponse app hook is gone (v2 only has onRequest/onResponse/onError), and onResponse's return value is ignored (toResponse does .then(() => response)), so the body can no longer be replaced through a hook.
• The response is now an immutable web Response.

Solution — dual support for h3 v1 and v2

• src/helper.ts: access send (v1) / toResponse (v2) dynamically via a namespace import so the module loads under both versions. compress falls back to mutating response.body when send is unavailable. Adds web-Response helpers compressResponse / compressResponseStream and a stream-aware getStreamCompression.
• src/middleware.ts (new): compression() and compressionStream() middleware for h3 v2 — they call next(), normalize the result with toResponse, and return a compressed Response. Optional forced method (e.g. compression('gzip')).
• src/index.ts: export the new middleware, helpers and types.
• peerDependencies: widen h3 to ^1.6.0 || ^2.0.0 (devDep pinned to the real v2 2.0.1-rc.22; npm h3@2.0.0 is a deprecated stub).
• Tests: ported to h3 v2 — mockEvent for the mutable / Nitro path, a real new H3() app + supertest for the middleware. gzip/deflate/br covered. 15 tests pass, ~97% coverage, lint + build green.
• README: new "Usage (h3 v2)" section and middleware utilities.

Notes

• The only uncovered branch is the v1 send path (not reachable when tested under v2); it is byte-identical to the previously shipped code.
• CI currently runs against v2 only. Happy to add an h3: [1, 2] matrix dimension if preferred.

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