Create Write-an-Extension.md

Write-an-Extension.md

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+🆕 Setup Extensions: Host + Options Support
+-------------------------------------------
+The Setup Extensions system now supports extended script metadata in the header.  
+This allows script authors to define dropdown menus and control how the script is executed.
+
+✅ New Metadata Parameters:
+
+  # Description: <string>
+     • Short, user-friendly description of what the script does.
+     • Displayed in the Extensions page below the title.
+
+  # Host: embedded | console
+     • embedded = run inside OOBE, output is captured and shown in the app.
+     • console  = run in an external PowerShell window with -NoExit.
+     • Default: embedded (if not specified).
+
+  # Options: value1; value2; value3; ...
+     • Defines multiple selectable actions for a single script.
+     • A dropdown is automatically shown in the Extensions page.
+     • The selected value is passed to the script as $choice.
+
+Example Script Header:
+
+  # Description: File Explorer tweaks
+  # Host: embedded
+  # Options: Show file extensions; Hide file extensions; Open This PC
+
+  param([string]$choice)
+  switch ($choice) {
+      "Show file extensions" { ... }
+      "Hide file extensions" { ... }
+      "Open This PC" { ... }
+  }
+
+-------------------------------------------
+With this update, one script can now provide multiple user actions,
+and devs can control whether output stays inside the OOBE app 
+or opens in a real console window.