Unclear active tab

[gauntface]

I love the theme, however I often find myself getting confused with what the active tab is.

Changing the active tab border to the bottom makes a big different:

Changing the bg to a light color is an extra step:

Is there any interest in making this change (I'm happy to raise a PR if so)?

NOTE: If you want to test this out quickly on your vscode, you can add the following to your settings.json:

"workbench.colorCustomizations": {
  "tab.activeBorder": "#FF79C6",
  "tab.activeBackground": "#343746",
}