Add readme example

Author: jlukic

README.md

@@ -4,6 +4,18 @@
 
 This **[Astro integration](https://astro.build/integrations/)** enables server-side rendering and client-side hydration for your [Lit](https://lit.dev/) custom elements.
 
+## How To Use
+
+```javascript
+import lit from '@semantic-ui/astro-lit';
+
+export default defineConfig({
+  integrations: [
+    lit(), // add lit as integration
+  ],
+});
+```
+
 ## License
 
 MIT