docs: add contribution guide

docs/content/1.get-started/4.contributing.md

@@ -0,0 +1,29 @@
+---
+title: Contributing
+description: We can never thank you enough for your contributions. ❤️
+---
+
+::callout
+It is highly recommended to read [Nuxt contribution guide](https://nuxt.com/docs/community/contribution) before making any contributions.
+::
+
+## How to contribute?
+
+- Clone [nuxt/image](https://github.com/nuxt/image) repository
+- Enable Corepack using `corepack enable`
+- Install dependencies using `pnpm install`
+- Run `pnpm dev:prepare` to generate type stubs.
+
+### Nuxt Image
+
+- Use `pnpm dev` to start the [playground](https://github.com/nuxt/image/tree/main/playground) in development mode.
+- Apply your changes
+- Add tests into the [test/](https://github.com/nuxt/image/tree/main/test) directory and run `pnpm test` to make sure they pass.
+- Check the code style with `pnpm lint`
+- Before creating a PR, make sure to run `pnpm build` and that no errors are reported.
+
+### Documentation
+
+- Use `pnpm dev:docs` to start the [documentation](https://github.com/nuxt/image/tree/main/docs) in development mode.
+- Open [http://localhost:3000](http://localhost:3000) to view it in the browser.
+- Update the content of the documentation in the [docs/content/](https://github.com/nuxt/image/tree/main/docs/content) directory.