Insufficient typing for `add`, `subtract`, `dotMultiply` etc

The functions
* [`add`](https://github.com/josdejong/mathjs/blob/develop/types/index.d.ts#L770)
* [`subtract`](https://github.com/josdejong/mathjs/blob/develop/types/index.d.ts#L1119)
* [`dotDivide`, `dotMultiply`, `dotPow` etc.](https://github.com/josdejong/mathjs/blob/develop/types/index.d.ts#L837)

lack sufficiently fine-grained type definitions. In particular, this produces an error:
```typescript
math.add([1, 2], [3, 4])[0];
// Element implicitly has an 'any' type because expression
// of type '0' can't be used to index type 'MathType'.
// Property '0' does not exist on type 'MathType'
```
while it should be clear that the result is a one-dimensional array.

Adding some overloads would make the TypeScript experience with Mathjs much smoother.