docs: add comprehensive installation guide for Roo Code extension

Author: hannesrudolph

docs/getting-started/installing.md docs/getting-started/installing.mdxdocs/getting-started/installing.md renamed to docs/getting-started/installing.mdx

@@ -4,6 +4,22 @@ sidebar_label: Installing Roo Code
 
 # Installing Roo Code
 
+<div style={{ position: 'relative', paddingBottom: '56.25%', height: 0, overflow: 'hidden' }}>
+  <iframe
+    src="https://www.youtube.com/embed/Mcq3r1EPZ-4"
+    style={{
+      position: 'absolute',
+      top: 0,
+      left: 0,
+      width: '100%',
+      height: '100%',
+    }}
+    frameBorder="0"
+    allow="autoplay; encrypted-media"
+    allowFullScreen
+  ></iframe>
+</div>
+
 Roo Code is a VS Code extension that brings AI-powered coding assistance directly to your editor. Install using one of these methods:
 1. **VS Code Marketplace (Recommended)** - fastest method for standard VS Code and Cursor users
 2. **Open VSX Registry** - for VS Code-compatible editors like VSCodium