Tab group does not support gap property.

[julczka]

Which exact UI Library version are you using? For example: 1.0.1 - don't just write v1.

1.6.0-rc-3

Bug summary

uui-tab group does not support gap property on it.
The #calculateBreakpoints method, responsible for setting the width on uui-tab-group, takes to account only widths of each uui-tab element, but not their margings or a gap property set on the uui-tab-group

Specifics

On the image below you can see a use case from cloud portal, where the layout of tabs is broken due to width set on the tab group

Steps to reproduce

follow the story added in PR #708

Expected result / actual result

It is possible to use tabs with a gap property on uui-tab-group