Accessibility: Add Landmark navigation (#12190)

Co-authored-by: R Midhun Suresh <hi@midhun.dev>

src/Keyboard.ts

@@ -29,6 +29,7 @@ export const Key = {
     ARROW_DOWN: "ArrowDown",
     ARROW_LEFT: "ArrowLeft",
     ARROW_RIGHT: "ArrowRight",
+    F6: "F6",
     TAB: "Tab",
     ESCAPE: "Escape",
     ENTER: "Enter",
@@ -77,6 +78,7 @@ export const Key = {
 };
 
 export const IS_MAC = navigator.platform.toUpperCase().includes("MAC");
+export const IS_ELECTRON = window.electron;
 
 export function isOnlyCtrlOrCmdKeyEvent(ev: React.KeyboardEvent | KeyboardEvent): boolean {
     if (IS_MAC) {