docs: add note for svelte v5 (#729)

Author: ota-meshi

README.md

@@ -4,6 +4,8 @@
 It provides many unique check rules by using the template AST.  
 You can check on the [Online DEMO](https://sveltejs.github.io/eslint-plugin-svelte/playground/).
 
+**_We are working on experimental support for Svelte v5, but may break with new versions of Svelte v5._**
+
 [![NPM license](https://img.shields.io/npm/l/eslint-plugin-svelte.svg)](https://www.npmjs.com/package/eslint-plugin-svelte)
 [![NPM version](https://img.shields.io/npm/v/eslint-plugin-svelte.svg)](https://www.npmjs.com/package/eslint-plugin-svelte)
 [![NPM downloads](https://img.shields.io/badge/dynamic/json.svg?label=downloads&colorB=green&suffix=/day&query=$.downloads&uri=https://api.npmjs.org//downloads/point/last-day/eslint-plugin-svelte&maxAge=3600)](http://www.npmtrends.com/eslint-plugin-svelte)

docs/README.md

@@ -8,6 +8,8 @@ title: 'eslint-plugin-svelte'
 It provides many unique check rules by using the template AST.  
 You can check on the [Online DEMO](./playground.md).
 
+**_We are working on experimental support for Svelte v5, but may break with new versions of Svelte v5._**
+
 [![NPM license](https://img.shields.io/npm/l/eslint-plugin-svelte.svg)](https://www.npmjs.com/package/eslint-plugin-svelte)
 [![NPM version](https://img.shields.io/npm/v/eslint-plugin-svelte.svg)](https://www.npmjs.com/package/eslint-plugin-svelte)
 [![NPM downloads](https://img.shields.io/badge/dynamic/json.svg?label=downloads&colorB=green&suffix=/day&query=$.downloads&uri=https://api.npmjs.org//downloads/point/last-day/eslint-plugin-svelte&maxAge=3600)](http://www.npmtrends.com/eslint-plugin-svelte)