Function getEndOfMonth

getEndOfMonth(date?: Date): undefined | Date
Returns the end month date of the given date
Parameters
- Optionaldate: Date
  the date to inspect
Returns undefined | Date
the end month date of the given date
Author
David Hsing
Example
```
getEndOfMonth(new Date(2023, 8, 1));    // Date(2023, 8, 30, 23, 59, 59)
```