Add riot-desktop shortcuts for forward/back matching browsers&slack

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/components/structures/LoggedInView.js

@@ -40,6 +40,7 @@ import {Resizer, CollapseDistributor} from '../../resizer';
 import MatrixClientContext from "../../contexts/MatrixClientContext";
 import * as KeyboardShortcuts from "../../accessibility/KeyboardShortcuts";
 import HomePage from "./HomePage";
+import PlatformPeg from "../../PlatformPeg";
 // We need to fetch each pinned message individually (if we don't already have it)
 // so each pinned message may trigger a request. Limit the number per room for sanity.
 // NB. this is just for server notices rather than pinned messages in general.
@@ -407,6 +408,11 @@ const LoggedInView = createReactClass({
                     });
                     handled = true;
                 }
+                break;
+
+            default:
+                // if we do not have a handler for it, pass it to the platform which might
+                handled = PlatformPeg.get().onKeyDown(ev);
         }
 
         if (handled) {