Stop using KeyboardEvent.keyCode as it is deprecated

src/Keyboard.js

@@ -1,6 +1,7 @@
 /*
 Copyright 2016 OpenMarket Ltd
 Copyright 2017 New Vector Ltd
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,52 +16,6 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-/* a selection of key codes, as used in KeyboardEvent.keyCode */
-export const KeyCode = {
-    BACKSPACE: 8,
-    TAB: 9,
-    ENTER: 13,
-    SHIFT: 16,
-    ESCAPE: 27,
-    SPACE: 32,
-    PAGE_UP: 33,
-    PAGE_DOWN: 34,
-    END: 35,
-    HOME: 36,
-    LEFT: 37,
-    UP: 38,
-    RIGHT: 39,
-    DOWN: 40,
-    DELETE: 46,
-    KEY_A: 65,
-    KEY_B: 66,
-    KEY_C: 67,
-    KEY_D: 68,
-    KEY_E: 69,
-    KEY_F: 70,
-    KEY_G: 71,
-    KEY_H: 72,
-    KEY_I: 73,
-    KEY_J: 74,
-    KEY_K: 75,
-    KEY_L: 76,
-    KEY_M: 77,
-    KEY_N: 78,
-    KEY_O: 79,
-    KEY_P: 80,
-    KEY_Q: 81,
-    KEY_R: 82,
-    KEY_S: 83,
-    KEY_T: 84,
-    KEY_U: 85,
-    KEY_V: 86,
-    KEY_W: 87,
-    KEY_X: 88,
-    KEY_Y: 89,
-    KEY_Z: 90,
-    KEY_BACKTICK: 223, // DO NOT USE THIS: browsers disagree on backtick 192 vs 223
-};
-
 export const Key = {
     HOME: "Home",
     END: "End",
@@ -80,13 +35,35 @@ export const Key = {
     SHIFT: "Shift",
     CONTEXT_MENU: "ContextMenu",
 
+    COMMA: ",",
     LESS_THAN: "<",
     GREATER_THAN: ">",
     BACKTICK: "`",
     SPACE: " ",
+    A: "a",
     B: "b",
+    C: "c",
+    D: "d",
+    E: "e",
+    F: "f",
+    G: "g",
+    H: "h",
     I: "i",
+    J: "j",
     K: "k",
+    L: "l",
+    M: "m",
+    N: "n",
+    O: "o",
+    P: "p",
+    Q: "q",
+    R: "r",
+    S: "s",
+    T: "t",
+    U: "u",
+    V: "v",
+    W: "w",
+    X: "x",
     Y: "y",
     Z: "z",
 };