Remove deepcopy dependency

src/@types/deepcopy.d.ts

@@ -1,17 +0,0 @@
-declare module 'deepcopy';
-
-declare namespace deepcopy {
-	type DeepcopyCustomizerValueType = 'Object';
-
-	type DeepcopyCustomizer<T> = (
-		value: T,
-		valueType: DeepcopyCustomizerValueType) => T;
-
-	interface DeepcopyOptions<T> {
-		customizer: DeepcopyCustomizer<T>;
-	}
-
-	export function deepcopy<T>(
-		value: T,
-		options?: DeepcopyOptions<T> | DeepcopyCustomizer<T>): T;
-}