feat: ArrayBuffer - String converter

@sammo/util/src/index.ts

@@ -45,4 +45,18 @@ export function isBufferSource(obj: unknown): obj is BufferSource {
 
 export function isNotNull<T>(value: T|null|undefined):value is T{
     return value !== null && value !== undefined;
+}
+
+export function ArrayBufferFromString(str: string): ArrayBuffer {
+	const enc = new TextEncoder();
+	const u8arr = enc.encode(str);
+	if(u8arr.buffer.byteLength === u8arr.byteLength){
+		return u8arr.buffer;
+	}
+	return u8arr.buffer.slice(u8arr.byteOffset, u8arr.byteOffset + u8arr.byteLength);
+}
+
+export function StringFromArrayBuffer(buffer: BufferSource): string {
+	const dec = new TextDecoder();
+	return dec.decode(buffer);
 }