First of all, thank you for the tab bar and tab line implementation in
Emacs 27.1. While using the feature, I found a possible improvement: Add
support for horizontal scrolling if your mouse or trackpad supports
it. The motivation for this change is that, as the tab line is a
horizontal UI, it makes sense to support horizontal scrolling if the
hardware supports it, as the scrolling feels more natural.

If you agree with the proposed feature, I've attached a patch that
implements it. Feel free to leave any review comments.