issues with finally on react-native

[chrisdrackett]

I'm attempting to use mst-gql on react native and I've run into the following:

TypeError: new Promise(function (resolve, reject) {
      this$1.onResolve = resolve;
      this$1.onReject = reject;
    }).finally is not a function. (In 'new Promise(function (resolve, reject) {
      this$1.onResolve = resolve;
      this$1.onReject = reject;
    }).finally(function () {
      this$1.store.ssr && this$1.store.unpushPromise(this$1.promise);
    })', 'new Promise(function (resolve, reject) {
      this$1.onResolve = resolve;
      this$1.onReject = reject;
    }).finally' is undefined)

I think this might be related to: facebook/react-native#17972

I'm going to spend a little time on it today, but figured it was worth opening the issue

[chrisdrackett]

I can confirm that removing the finally fixes the issue on react-native. I'm pretty behind on promises in general, so I'll open a PR with a fix that might not be ideal :D