feat(previews): add refreshAllPreviews method to refresh all previews

This commit introduces the `refreshAllPreviews` method in the `PreviewsStore` class, which iterates through all previews and triggers a file change broadcast for each. This ensures that all previews are updated after a file save operation.

refactor(CodeBlock): handle unsupported languages by falling back to plaintext

The `CodeBlock` component now defaults to 'plaintext' when an unsupported language is detected, improving the user experience by avoiding unsupported language errors.

prompts: update dependency installation instructions

The prompts documentation has been updated to clarify the process of installing dependencies, emphasizing the importance of updating `package.json` first and avoiding individual package installations.

app/lib/stores/previews.ts

@@ -295,6 +295,18 @@ export class PreviewsStore {
 
     this.#refreshTimeouts.set(previewId, timeout);
   }
+
+  refreshAllPreviews() {
+    const previews = this.previews.get();
+
+    for (const preview of previews) {
+      const previewId = this.getPreviewId(preview.baseUrl);
+
+      if (previewId) {
+        this.broadcastFileChange(previewId);
+      }
+    }
+  }
 }
 
 // Create a singleton instance