Missing doc: Orphan Resource Explorer

**Your Godot version:**
4.2.1-stable

**Issue description:**
Orphan Resource Explorer has absolutely no documentation.
One can only guess at what it's for and what the columns mean.
https://docs.godotengine.org/en/stable/search.html?q=%22Orphan+Resource+Explorer%22&check_keywords=yes&area=default#

**URL to the documentation page (if already existing):**
N/A