-go-to-definitions (OGTD file format)

src/entity.cpp

@@ -91,6 +91,7 @@ struct Entity {
 	Ast *       identifier; // Can be nullptr
 	DeclInfo *  decl_info;
 	DeclInfo *  parent_proc_decl; // nullptr if in file/global scope
+	AstFile *   file;
 	AstPackage *pkg;
 
 	// TODO(bill): Cleanup how `using` works for entities