Added Helper Scripts section of FFU Builder docs site

Added new docs for Create-PEMedia.ps1 and USBImagingToolCreator.ps1 files to help explain how to use the scripts.

docs/helper_scripts.md

@@ -0,0 +1,20 @@
+---
+title: Helper Scripts
+nav_order: 4
+prev_url: /ui_overview.html
+prev_label: UI Overview
+next_url: /create_pemedia.html
+next_label: Create PE Media
+has_children: true
+has_toc: false
+---
+# Helper Scripts
+
+This section documents standalone helper scripts used outside the primary UI-driven build workflow.
+
+## Available helper scripts
+
+- [Create PE Media](/create_pemedia.html)
+- [USB Imaging Tool Creator](/usb_imaging_tool_creator.html)
+
+{% include page_nav.html %}