feat: --background-selected property for ion-tab-button

[donhmorris]

Prerequisites

• I have read the Contributing Guidelines.
• I agree to follow the Code of Conduct.
• I have searched for existing issues that already include this feature request, without success.

Describe the Feature Request

Would like to be able to set the background color for selected tab in and ion-tab-bar.
There is a custom property for setting the color in ion-tab-button (--color-selected). Would be helpful to have a correlating custom property for the background-color (with an rgba value) when the button is selected.

Describe the Use Case

When a tab-bar-button is selected, the background color is specified by a custom property.

Describe Preferred Solution

Add a --background-color-selected custom property to ion-tab-button.

Describe Alternatives

No response

Related Code

No response

Additional Information

No response