[fetch] PATCH verb (#50)

Should the patch verb be included in the spec? (https://tools.ietf.org/html/rfc5789)

here -
https://fetch.spec.whatwg.org/#methods#concept-method-normalize

and
https://fetch.spec.whatwg.org/#http-network-or-cache-fetch
```
If request's body is null and request's method is `HEAD`, `POST`, or `PUT`, set contentLengthValue to `0`.
```

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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/50