Gradient color for Borders / New feature

- [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.**

Great if you add gradient color to border settings. At the moment we can only apply simple color on borders. Adding this feature removes this limitation. Gradient colors are widely used in modern sites.

thank you