[suggestion] Provide coverage for more Simple Line Icons in free version
In the upgrade from CoreUI 2 to CoreUI 3,  the recommendation is to stop using FontAwesome, and [Simple Line Icons](https://simplelineicons.github.io/), and to start using CoreUI icons.

This is great however it comes at a cost: You lose access to a significant amount of icons.

It would be a great contribution to your dedication to open source if the free set of CoreUI icons included replacements for more of the icons that were provided by Simple Line Icons.

Given the Simple Line Icons contains <180 icons, and most of the ones missing from the free version do exist in the pro version of CoreUI icons, this would largely be a judgement call and business decision on your end that I hope you can consider.

Some of the ones that would be valuable replacements for Simple Line Icons to include in the free version:

* https://coreui.io/icons/linear/check-circle/
* https://coreui.io/icons/linear/plus-circle/
* https://coreui.io/icons/linear/minus-circle/
* https://coreui.io/icons/linear/exclamation-circle/
* https://coreui.io/icons/linear/chevron-left-alt/
* https://coreui.io/icons/linear/chevron-right-alt/
* https://coreui.io/icons/linear/chevron-bottom-alt/
* https://coreui.io/icons/linear/chevron-top-alt/
* https://coreui.io/icons/linear/key-alt/
* https://coreui.io/icons/linear/eye/
* https://coreui.io/icons/linear/shield-x/
* https://coreui.io/icons/linear/check-alt/ (Issue #6)
* https://coreui.io/icons/linear/check-circle/
* Help, Question mark, Question mark circle (Issue #5)
* Info circle.
* Rocket
* https://coreui.io/icons/linear/globe/
* https://coreui.io/icons/linear/signpost/

Thanks!