docs: add knowledge base

docs/kb_sections/dzg004.adoc

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+[[DZG-004, DZG-004]]
+== DZG-004: On Steam Deck, some mods in the Workshop show a black screen when DZGUI attempts to open them
+Last updated: {d}
+
+This is a bug in the Steam client that is being tracked at Valve's Steam for Linux issue tracker https://github.com/ValveSoftware/steam-for-linux/issues/9598[here].
+
+To resolve this issue, manually intervene in the Steam client by selecting a different context (e.g., Store, Library), waiting for it to load, then navigating back to the Workshop context. This should clear the blockage and allow the contents to render.