Function throttle

throttle(func: () => void, rateMs: number): () => void
Make the given function a throttled one.
Parameters
- func: () => void
- rateMs: number
Returns () => void
Example
```
const func = throttle( 100, () => {
  // some expensive procedure
} );

func();
func();
func();
```
- Defined in throttle.ts:15