feat: add demos for svelte

Author: yangfuhai

demos/svelte-ts/.gitignore

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+node_modules
+
+# Output
+.output
+.vercel
+/.svelte-kit
+/build
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Env
+.env
+.env.*
+!.env.example
+!.env.test
+
+# Vite
+vite.config.js.timestamp-*
+vite.config.ts.timestamp-*

demos/svelte-ts/.npmrc

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+engine-strict=true

demos/svelte-ts/README.md

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+# create-svelte
+
+Everything you need to build a Svelte project, powered by [`create-svelte`](https://github.com/sveltejs/kit/tree/main/packages/create-svelte).
+
+## Creating a project
+
+If you're seeing this, you've probably already done this step. Congrats!
+
+```bash
+# create a new project in the current directory
+npm create svelte@latest
+
+# create a new project in my-app
+npm create svelte@latest my-app
+```
+
+## Developing
+
+Once you've created a project and installed dependencies with `npm install` (or `pnpm install` or `yarn`), start a development server:
+
+```bash
+npm run dev
+
+# or start the server and open the app in a new browser tab
+npm run dev -- --open
+```
+
+## Building
+
+To create a production version of your app:
+
+```bash
+npm run build
+```
+
+You can preview the production build with `npm run preview`.
+
+> To deploy your app, you may need to install an [adapter](https://kit.svelte.dev/docs/adapters) for your target environment.