SnapHeal: Click-Cast Healing

#r13
- Fixed: Target keybinds (assigned to any mouse button/key, with or without modifiers like Ctrl/Shift) now work correctly - previously they only worked on plain left-click.
- Removed: "Context Menu" as an assignable keybind action. It's no longer selectable in the keybind dropdown, since there's no reliable way to trigger it outside of a plain, unmodified right-click. Right-click still opens the context menu by default when nothing else is bound to it.