Feat: monocle mode

[Fuann-Kinoko]

Hi, I've tried to add a simple monocle implementation #78 that doesn't involve any modifications to the existing tiling window logic.

Instead of defining new monocle containers, it just draws each tiling window (floating windows are ignored) in the workspace where isMonocle is set to true, to fit most of the screen (the same size as the rectangle of a tiled window with a 100% size percentage). If the isMonocle flag is set to false, then GlazeWM restores the position of the managed windows correctly, since they were never touched or modified in monocle mode.

And because there are only two directions in Monocle mode: next/prev, I've also added two commands: focus next/prev to focus the corresponding window in the nested window tree (they're essentially the same as focusInDirection, but less restrictive), and an override of hjkl to focus next/prev when the workspace is in monocle mode.

This implementation can be tested by adding a keyboard binding to the command toggle monocle (focus next and focus prev is also added).

[Fuann-Kinoko]

bar component monocle indicator added for convenience

    - type: "monocle indicator"
      label_entered: "󰊓"
      label_exited: " "
      foreground: "#b4637a"

[lars-berger]

Due to the C# -> Rust rewrite, some of these older PRs aren't compatible anymore. Can't merge as is, and I'm sorry about not finding the time to get this in while the C# version was active. Nevertheless, thank you for contributing to GlazeWM 🙏