Fix: use editUrl function to correct PXF doc edit links

[tuhaihe]

The string-form editUrl appended the project-relative path (pxf/docs/*.md) instead of the plugin-relative path, resulting in broken "Edit this page" URLs on the PXF docs site. Switch to the function form so docPath is correctly relative to the plugin's path option (pxf/docs).

closes: #ISSUE_Number

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