Add extension to detect unused images

[rosieyohannan]

Unused Media Detection Extension

Problem - we have unused images that need to be archived

There is an extension to detect unused media: https://github.com/bonitasoft/antora-detect-unused-media-extension but it flags many images as unused that were actually in use.

Issues with the existing extenstion

1. Missing Cross-Component Reference Support - The original extension only checked for:

• images/myImage.png
• ROOT:images/myImage.png (module)

But we use cross-component references like:

• guides:ROOT:images/myImage.png

2. Regex Pattern

The regex /(image|video)::?([^[]+)/g was matching our images but also some content from CircleCI code blocks, for example: image: cimg/base:2021.04

When it hit YAML image: keys, it would capture everything until the next [ character, creating mangled references that included large chunks of documentation content.

3. Missing Implicit images/ Directory Handling. In Antora/AsciiDoc, the images/ directory is implicit. References like guides:ROOT:core_dumps.png actually point to modules/ROOT/images/core_dumps.png but the extension wasn't checking both formats.

Fix

Created a custom local extension at extensions/detect-unused-media-extension.js with the following fixes:

1. Improved Regex Pattern:

• Matches only non-whitespace characters (\S+?)
• Stops at [ or end of line
• Uses multiline mode to prevent cross-line matching

2. Docker Image Filtering

3. Comprehensive Path Checking

The extension now checks 6 different reference formats for each image:

• images/myImage.png (full path with images/)
• myImage.png (without images/ - implicit)
• ROOT:images/myImage.png (module-qualified with images/)
• ROOT:myImage.png (module-qualified without images/)
• guides:ROOT:images/myImage.png (component-qualified with images/)
• guides:ROOT:myImage.png (component-qualified without images/)

Archived Unused Images

Created archive/images/ directory and moved unused images to archive. We can be sure this is working because the build will fail if a referenced image is missing.