SELECT2 Optgroup

## Prerequisites

- [x] I have searched for similar features requests in both open and closed tickets and cannot find a duplicate.
- [x] The feature is still missing in the latest stable version of Elementor ( Elementor Pro. )

**What problem is your feature request going to solve? Please describe.**
The possibility to have optgroup in **SELECT2**.

**Describe the solution you'd like**
I would like to have the possibility to defined groups for **SELECT2** as i have for **SELECT**
I know it fully supported by SELECT2 but i missing it for Widget Development

**Describe alternatives you've considered**
At the moment i only have to use **SELECT** but not giving me the search feature as **SELECT2**