Function isNull

isNull(value: unknown): value is null
Check if a value is null.
Parameters
- value: unknown
  The value to check
Returns value is null
Example
```
import { isNull } from '@aws-lambda-powertools/commons/typeUtils';

const value = null;
if (isNull(value)) {
  // value is null
}
```
- Defined in typeUtils.ts:134