Add Crusader-specific USECODE data and documentation

- Introduced new file `vm_mask_ladder.tsv` containing detailed mappings for Crusader USECODE VM masks and their associated descriptors.
- Added comprehensive documentation in `scummvm-crusader-reference.md` outlining the structure, findings, and implications for reverse-engineering the Crusader engine within ScummVM.
- Created `usecode-roundtrip-ir.md` to document the plan for converting Crusader USECODE bytes into a human-readable format, detailing the container layout, event names, and intrinsic tables.
- Implemented a PowerShell script `temp_usecode_sample.ps1` for extracting and analyzing USECODE data from the Crusader FLX files, providing insights into class and event structures.

Crusader_Decomp.code-workspace

@@ -5,6 +5,9 @@
 		},
 		{
 			"path": "../../mcp/GhidraMCP"
+		},
+		{
+			"path": "../../misc/scummvm"
 		}
 	],
 	"settings": {