new: add community-maintained extension package explanation

[Myxogastria0808]

The author should do the following, if applicable

This PR adds a short section to the @hono/zod-openapi README introducing a community-maintained extension, zod-openapi-share, which helps centralize and reuse common OpenAPI response definitions.

The extension is clearly marked as non-official and is intended to complement @hono/zod-openapi in real-world API development.

• Add tests
• Run tests
• yarn changeset at the top of this repo and push the changeset
• Follow the contribution guide

[changeset-bot]

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[Copilot]

Pull request overview

Adds documentation to the @hono/zod-openapi package README to point users to a community-maintained extension for sharing/reusing OpenAPI response definitions.

Changes:

• Introduces a new “Community Extensions” section in the @hono/zod-openapi README
• Adds a short description and links for the zod-openapi-share community package

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[Copilot]

In prose, "hono" is referred to elsewhere in this README as the framework name "Hono". Consider capitalizing it here for consistency (the package name can remain hono when referring to npm/install).

Suggested change

	Normally, `@hono/zod-openapi` requires you to redefine the same responses (e.g., error schemas) for every endpoint, but with `zod-openapi-share`, you can avoid repetition and prevent definition drift, making your backend development using `hono` + `@hono/zod-openapi` cleaner and more consistent.
	Normally, `@hono/zod-openapi` requires you to redefine the same responses (e.g., error schemas) for every endpoint, but with `zod-openapi-share`, you can avoid repetition and prevent definition drift, making your backend development using Hono + `@hono/zod-openapi` cleaner and more consistent.

[Copilot]

These bullets use raw URLs; elsewhere in this README links are typically formatted as Markdown links (e.g., ## References uses - [Hono](https://hono.dev/) around lines 542–546). Consider switching these to Markdown link syntax for consistency/readability.

Suggested change

	- GitHub: https://github.com/Myxogastria0808/zod-openapi-share
	- npm: https://www.npmjs.com/package/zod-openapi-share
	- GitHub: [Myxogastria0808/zod-openapi-share](https://github.com/Myxogastria0808/zod-openapi-share)
	- npm: [zod-openapi-share](https://www.npmjs.com/package/zod-openapi-share)