Add make target to run validation against local specifications.xlsx file

Author: m-houston

Makefile

@@ -30,6 +30,9 @@ internal-config:
 	npm run parse --workspace=@supplier-config/excel-parser -- \
 		"$(PWD)/specifications.xlsx" --output-dir "$(PWD)/artifacts/config-store" --pretty
 
+validate-config:
+	npm run parse --workspace=@supplier-config/excel-parser -- \
+		"$(PWD)/specifications.xlsx" --check-mappings
 # ==============================================================================
 
 ${VERBOSE}.SILENT: \