Enable TAB to access emulator

While in the IDE:
- (NEW) Use ESC, then TAB to focus emulator
- (Existing) Use ESC, then SHIFT-TAB to access sidenav

src/common/emu.ts

@@ -32,7 +32,7 @@ export function __createCanvas(doc:HTMLDocument, mainElement:HTMLElement, width:
   canvas.width = width;
   canvas.height = height;
   canvas.classList.add("emuvideo");
-  canvas.tabIndex = -1;               // Make it focusable
+  canvas.tabIndex = 0; // Make it focusable and tabbable
   mainElement.appendChild(canvas);
   return canvas;
 }