remove use of __proto__

[nitsky]

Hi, node recently added a --disable-proto option to disable use of __proto__ due to security issues: nodejs/node#32279. Similarly, deno also recently removed support for __proto__: denoland/deno#4341. Would you consider removing the use of __proto__ in this package? The changes proposed in #10 would take care of it if merged.

[adrianheine]

Using Object.getPrototypeOf if available should be a viable workaround.