Function parse_key 

pub fn parse_key(notation: &str) -> Result<KeyCombo, String>

Parse key notation string into a KeyCombo.

Format: [modifier-]*key Modifiers: C (Ctrl), S (Shift), A (Alt) Keys: single char, F1–F12, Space, Tab, Enter, Esc

Examples:

• C-s → Ctrl+S
• C-S-s → Ctrl+Shift+S
• A-p → Alt+P
• F5 → F5
• C-Space → Ctrl+Space