feat: Add query selector for style rules

This commit introduces the ability to select style rules by query
selector. This feature enhances the flexibility of style rule
selection in Svelte. The README has been updated with examples
and usage instructions.

Author: ryoppippi

README.md

@@ -44,5 +44,44 @@ contents of b.css will be here
 </style>
 ```
 
+### Select Style Rules by Query Selector
+
+You can select style rules by query selector.
+
+For example, the following CSS and Svelte:
+
+
+```css
+/* a.css */
+
+div { color: red; }
+
+.message { color: blue; }
+```
+
+```svelte
+<div> hello </div>
+<p class="message"> world </p>
+
+<style>
+@import "./a.css?.message" scoped;
+
+div { color: green; }
+</style>
+```
+
+will get converted into:
+
+```svelte
+<div> hello </div>
+<p class="message"> world </p>
+
+<style>
+.message { color: blue; }
+
+div { color: green; }
+</style>
+```
+
 ## License
 [MIT](./LICENSE)