Fix transparent urlbar with ATBC

[PixsaOJ]

fixes #16

Fixes issue of URLbar sometimes being transparent.

If you are using ATBC extension to have different theme for each website and you also use popup URLbar, then you might need this fix.

This just sets the colors, but it might not match with link suggestion box's background (I'm talking about whats under URLbar).
You would also need to set this settings in extension preferences, here is mine:

Notice that Toolbar background setting is 1 tick higher than tab bar setting.

Tested on FR 123.0.1

[jacksonsamuelmoore]

Fantastic - fixes the transparency issue! However I tested and found that there's a second instance of --toolbar-bgcolor being used just below this that also needs to be changed, otherwise the URL bar suggestions container colour might not match the URL bar colour like so:

[PixsaOJ]

I noticed that --toolbar-bgcolor and did not know what it was for. I am able to adjust that using extension settings.

I will go ahead and include that as well