Add Windows PowerShell example in Compiling with PCK encryption key

(cherry picked from commit 6de096dd8341836a64b95fcadec9570782bd776f)

development/compiling/compiling_with_script_encryption_key.rst

@@ -45,10 +45,14 @@ Step by step
 
        export SCRIPT_AES256_ENCRYPTION_KEY="your_generated_key"
 
-    .. code-tab:: bat Windows
+    .. code-tab:: bat Windows (cmd)
 
        set SCRIPT_AES256_ENCRYPTION_KEY=your_generated_key
 
+    .. code-tab:: bat Windows (PowerShell)
+
+       $env:SCRIPT_AES256_ENCRYPTION_KEY="your_generated_key"
+
 3. Compile Godot export templates and set them as custom export templates
    in the export preset options.