Add config options for exclusive zone and input event passthrough

[alebastr]

So I sneakily added the overlay layer value in one of the previous PRs, but it wasn't behaving as a real overlay mode of swaybar. Here's the two missing bits: input passthrough flag that makes the bar ignore any pointer events and allows the window underneath to handle those, and a flag to disable the exclusive zone.

Possible uses:

• A bar on the bottom layer with "exclusive": false which is only visible on an empty workspace.
• A transparent bar on the overlay or top layer which shows some data over the application window, but cannot be interacted with.
• If you look closely at the swaybar hide mode (the one where you only see a bar when the binding is pressed), it actually does not set exclusive zone but still accepts input.
  Now we can get almost similar behavior with creative use of bindsym --no-repeat, bindsym --no-repeat --release and SIGUSR1. With possibility of races, bar states out of sync between different screens and other wonderful bugs.

Fixes #1091

[Alexays]

Thanks again @alebastr ❤️
Can you update the Github wiki with these man changes?

[alebastr]

Can you update the Github wiki with these man changes?

Updated.