Add keypad values in keyToCharacterMapping

using Unicode COMBINING ENCLOSING KEYCAP

(cherry picked from commit 4cdf170)

Sources/KeyboardShortcuts/Shortcut.swift

@@ -185,7 +185,30 @@ private var keyToCharacterMapping: [KeyboardShortcuts.Key: String] = [
  .f17: "F17",
  .f18: "F18",
  .f19: "F19",
- .f20: "F20"
+ .f20: "F20",
+
+ // Representations for numeric keypad keys with ⃣ Unicode U+20e3 'COMBINING ENCLOSING KEYCAP'
+ .keypad0: "0\u{20e3}",
+ .keypad1: "1\u{20e3}",
+ .keypad2: "2\u{20e3}",
+ .keypad3: "3\u{20e3}",
+ .keypad4: "4\u{20e3}",
+ .keypad5: "5\u{20e3}",
+ .keypad6: "6\u{20e3}",
+ .keypad7: "7\u{20e3}",
+ .keypad8: "8\u{20e3}",
+ .keypad9: "9\u{20e3}",
+ // There's "⌧“ 'X In A Rectangle Box' (U+2327), "☒" 'Ballot Box with X' (U+2612), "×" 'Multiplication Sign' (U+00d7), "⨯" 'Vector or Cross Product' (U+2a2f), or a plain small x. All combined symbols appear bigger.
+ .keypadClear: "☒\u{20e3}", // The combined symbol appears bigger than the other combined 'keycaps'
+ // TODO: Respect locale decimal separator ("." or ",")
+ .keypadDecimal: ".\u{20e3}",
+ .keypadDivide: "/\u{20e3}",
+ // "⏎" 'Return Symbol' (U+23CE) but "↩" 'Leftwards Arrow with Hook' (U+00d7) seems to be more common on macOS.
+ .keypadEnter: "↩\u{20e3}", // The combined symbol appears bigger than the other combined 'keycaps'
+ .keypadEquals: "=\u{20e3}",
+ .keypadMinus: "-\u{20e3}",
+ .keypadMultiply: "*\u{20e3}",
+ .keypadPlus: "+\u{20e3}"
 ]
 
 private func stringFromKeyCode(_ keyCode: Int) -> String {