Style the omnibar different when a new tab is going to be opened

[ManuelTS]

When the omnibar is displayed by a shortcut for a new tab, render it visually different than the omnibar replacing the URL of the current tab. Possible solutions from the top of my head:

• • as prefixed icon before the omnibar text or input
• t+ as prefixed icon before the omnibar text or input

As I think of that, you maybe to the exact opposite, render the replace-current-tab omnibar with as vim's :ls command displays its files:

• "a" as prefixed icon before the omnibar text or input to signal that the current active tab will be affected by choosing an URL

[UncleSnail]

I also like this idea. If @philc agrees that it is good, I can take over implementing it if @ManuelTS would like.
Another option if we don't want to add a prefix by default would be to add a class to the vomnibar for each action that opened it. This would allow custom styles to be added to each vomnibar type and would allow users to change the color of the input box or add a prefix with :before text.

[ManuelTS]

I see you are definitely more in the code as me, feel free to take over and to take off ;)