Function isFirstDayOfMonth

isFirstDayOfMonth(date?: Date): boolean
Returns whether the given date is the first day of month
Parameters
- Optionaldate: Date
  The date to check
Returns boolean
whether the date is the first day of month
Author
David Hsing
Example
```
isFirstDayOfMonth(new Date(2023, 8, 1));    // true
isFirstDayOfMonth(new Date(2023, 8, 30));    // false
```