[zjdangge]

Local links are resolved against source files even when a resource mapping copies them to another output directory. Add a worked example showing how ~/, src, and dest interact, including the InvalidFileLink warning caused by linking to the output path.

Relates to #11030.

Validation:

• Built the current DocFX CLI for net10.0 in Release (0 warnings, 0 errors).
• Reproduced the warning with the issue's destination-path link; source-root and relative source links both built without warnings and resolved to the copied image.
• Built the exact documented JSON and Markdown example: 0 warnings, 0 errors; verified the generated image URL and output file.