TypeScript: Property 'invalidateStore' does not exist on type 'RecordSourceProxy'

When using `commitLocalUpdate` to invalidate the store the TS compiler throws and error:

```
Property 'invalidateStore' does not exist on type 'RecordSourceProxy'
```

You can reproduce by writing the following in a TypeScript project:

```
commitLocalUpdate(relayEnvironment, (store : RecordSourceProxy) => {
store.invalidateStore(); // Property 'invalidateStore' does not exist on type 'RecordSourceProxy'
});
```

I believe that `RecordSourceProxy` needs to be updated in `updater: StoreUpdater` to `RecordSourceSelectorProxy`.

If someone points me in the right direction on where to make this change, I can make a PR.