Implement a function that takes two promises and returns a single Promise that resolves only after both input promises have resolved.

Behavior requirements

When both promises fulfill, the returned promise must resolve to a single value, combining the two results according to their shared type.
- If both values are numbers, return their sum.
- If both values are strings, return their concatenation.
- If both values are arrays, return a new array containing all elements from both arrays (in order).
- If both values are plain objects, return a new object that merges the properties of both objects.

Error and rejection rules

If the two fulfillment values are not of the same supported type (number, string, array, or plain object), the returned promise must be rejected with the message 'Unsupported data types'.
If either of the input promises rejects, the returned promise must reject with the same rejection reason as that failed promise.

Examples

await promiseMerge(Promise.resolve(10), Promise.resolve(5)); // 15
await promiseMerge(Promise.resolve('hello '), Promise.resolve('world')); // 'hello world'
await promiseMerge(Promise.resolve(['x']), Promise.resolve(['y', 'z'])); // ['x', 'y', 'z']
await promiseMerge(Promise.resolve({ a: 1 }), Promise.resolve({ b: 2 })); // { a: 1, b: 2 }

await promiseMerge(Promise.resolve('1'), Promise.resolve(1)); // Rejected with 'Unsupported data types'
await promiseMerge(Promise.resolve({ a: 1 }), Promise.resolve()); // Rejected with 'Unsupported data types'

await promiseMerge(Promise.reject(new Error('Network')), Promise.resolve(2)); // Rejected with Error('Network')