mint-screenshot@khumnath: Add new screenshot and annotation applet

[khumnath]

New Applet: Mint Screenshot

A screenshot capture and annotation tool that integrates directly into the Cinnamon panel.

*Note: This is the Continuation of pull request #8560

What it does

Mint Screenshot combines screen capture and image annotation into a single workflow —
something the default screenshot tool (gnome-screenshot) doesn't offer. Instead of
capturing a screenshot and then opening a separate editor to annotate it, users can
draw, highlight, and add text directly on the captured image before saving.

Key features

• Capture modes: Fullscreen, area selection, timed capture (1–999s custom countdown)
• Annotation tools: Rectangle, ellipse, arrow, freehand draw, highlight, text — with 6 colors and adjustable line width
• Non-destructive editing: Move, resize, rotate, and delete any annotation after placing
• Export: Save as PNG/JPG/GIF with quality presets, or copy directly to clipboard
• Crop: Drag handles to adjust the capture region after taking the screenshot
• Keyboard shortcuts: Ctrl+S (save), Ctrl+C (copy), Ctrl+Z/Y (undo/redo), Delete (remove annotation)
• Cross-session: Works on both X11 (direct pixel capture) and Wayland (XDG Desktop Portal)
• HiDPI: Pixel-perfect rendering on scaled displays
• Dependencies: Auto-detected on first launch with distro-specific install instructions

Dependencies

Uses standard Python/GTK packages: python3-gi, python3-gi-cairo, python3-cairo, python3-pil, gir1.2-wnck-3.0 (X11), and python3-dbus (Wayland).