fix(api/global.d.ts): add 'await-to-js' type defs

Temporary fix until scopsy/await-to-js#47 is merged.

Author: nicholaschiang

lib/api/global.d.ts

@@ -0,0 +1,6 @@
+declare module 'await-to-js' {
+  export default function to<T, U = Error>(
+    promise: Readonly<Promise<T>>,
+    errorExt?: object
+  ): Promise<[U | null, T | undefined]>;
+}