Add auto pkg & run react runtimes tests against auto & transform runtimes

[andrewiggins]

Add auto package (not exported yet though) in preparation for next major release that will make auto runtime opt-in

Run @preact/signals-react test suite against test files using the auto and transform runtimes to verify each runtime's behavior.

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 907e043339a52bd83af0111745b86bae35fda08e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | --------------------- | ----- | | @preact/signals-react | Patch |

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Click here if you're a maintainer who wants to add another changeset to this PR

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[github-actions[bot]]

Size Change: -470 B (-1%)

Total Size: 83.6 kB

Filename	Size	Change
docs/dist/assets/client.********.js	46.8 kB	-145 B (0%)
packages/react/dist/signals.js	1.43 kB	-115 B (-7%)	✅
packages/react/dist/signals.mjs	1.34 kB	-210 B (-14%)	👏

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `docs/dist/assets/index.********.js` | 833 B | | `docs/dist/assets/jsxRuntime.module.********.js` | 281 B | | `docs/dist/assets/preact.module.********.js` | 4.02 kB | | `docs/dist/assets/signals-core.module.********.js` | 1.46 kB | | `docs/dist/assets/signals.module.********.js` | 2.02 kB | | `docs/dist/assets/style.********.js` | 21 B | | `docs/dist/assets/style.********.css` | 1.21 kB | | `docs/dist/basic-********.js` | 244 B | | `docs/dist/demos-********.js` | 3.35 kB | | `docs/dist/nesting-********.js` | 1.13 kB | | `docs/dist/react-********.js` | 239 B | | `packages/core/dist/signals-core.js` | 1.54 kB | | `packages/core/dist/signals-core.mjs` | 1.56 kB | | `packages/preact/dist/signals.js` | 1.27 kB | | `packages/preact/dist/signals.mjs` | 1.22 kB | | `packages/react-transform/dist/signals-*********.js` | 4.77 kB | | `packages/react-transform/dist/signals-transform.mjs` | 4.02 kB | | `packages/react-transform/dist/signals-transform.umd.js` | 4.88 kB |

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