extract deepFreeze function

src/Umbraco.Web.UI.Client/libs/observable-api/deep-freeze.function.ts

@@ -0,0 +1,18 @@
+export const deepFreeze = Object.freeze(function deepFreezeImpl<T>(inObj: T): T {
+	if (inObj != null && typeof inObj === 'object') {
+		Object.freeze(inObj);
+
+		Object.getOwnPropertyNames(inObj)?.forEach(function (prop) {
+			if (
+				// eslint-disable-next-line no-prototype-builtins
+				(inObj as any).hasOwnProperty(prop) &&
+				(inObj as any)[prop] != null &&
+				typeof (inObj as any)[prop] === 'object' &&
+				!Object.isFrozen((inObj as any)[prop])
+			) {
+				deepFreeze((inObj as any)[prop]);
+			}
+		});
+	}
+	return inObj;
+});