Support to theme the entire workbench

[SetTrend]

Currently, color themes are not getting applied to the toolbar on the left:

I tend to believe this is not intentional as it inhibits accessibility, e.g. with high-contrast themes.

So I propose to have themes apply to the VS Code toolbar, too.

[akamud]

+1. I get a lot of people asking for this for my theme. I assume a lot of theme developers do.