refactor(yaml): cleanup str type (#5879)

initial commit

yaml/_type/str.ts

@@ -6,11 +6,7 @@ import type { Type } from "../_type.ts";
 
 export const str: Type<"scalar", string> = {
   tag: "tag:yaml.org,2002:str",
-  resolve() {
-    return true;
-  },
-  construct(data): string {
-    return data !== null ? data : "";
-  },
   kind: "scalar",
+  resolve: (): boolean => true,
+  construct: (data: string | null): string => data !== null ? data : "",
 };