feat: adds screenshot plugin

[sandptel]

Objective

This Plugin adds support for fetching and saving screenshots using the wlr_screencopy.

struct ScreenshotEvent {
    pub capture_type: CaptureType,
    pub mouse_overlay: MouseOverlay,
    pub output_path: PathBuf,
}

EventWriter<ScreenshotEvent> can be used to write a screenshot-event { request a screenshot to a specific output_path }