Function isUndefined

isUndefined(value: unknown): value is undefined
Checks if value is undefined.
Parameters
- value: unknown
  The value to check.
Returns value is undefined
Returns true if value is undefined, else false.
Example
```
isUndefined(undefined)
// => true

isUndefined('Hello, world!')
// => false
```
- Defined in isUndefined.ts:18