Add types for fetch request

[shoonia]

We use the wix-fetch with request options like credentials and cache. May you add more request options to types.

And may you change property body, headers etc... as a not required property.

For example:

type RequestMode = "cors" | "no-cors" | "same-origin";

type RequestCredentials = "omit" | "include" | "same-origin";

type RequestCache =
    "default"
    | "force-cache"
    | "no-cache"
    | "no-store"
    | "only-if-cached"
    | "reload";

type WixFetchRequest = {

    method?: string;

    headers?: object;

    body?: string;

    mode?: RequestMode;

    credentials?: RequestCredentials;

    cache?: RequestCache;
};

Thanks!

• node-fetch types: https://npm.runkit.com/@types/node-fetch/index.d.ts?t=1568036747096

[shoonia]

moved this issue to corvid-types wix-incubator/corvid-types#15