Filip Zukal

@nakakura I do not know if the properties of `MIDIOptions` has to be required. According to [MDN](https://developer.mozilla.org/en-US/docs/Web/API/Navigator/requestMIDIAccess#midioptions) and [W3C](https://webaudio.github.io/web-midi-api/#MIDIOptions) they should, but in the [lib.dom.d.ts library:779](https://github.com/microsoft/TypeScript/blob/0b37062eb07d1666245a02471b7d0e80c5d5aa5d/src/lib/dom.generated.d.ts#L779) they are optionals.

Ready to merge

Hi @saschanaz, I forgot to write, sorry. I have to explicitly give `"lib": ["dom", "dom.iterable"]` to have these methods included, although the target is `ES2015+`.

> In that case that may be TypeScript bug, unless you already assigned other libs in the field. If you assigned any value in `lib` then it needs `dom` and...