enabled overview ruler by default in the demo

Author: AnouarTouati

demo/client.ts

@@ -256,6 +256,7 @@ function createTerminal(): void {
   const isWindows = ['Windows', 'Win16', 'Win32', 'WinCE'].indexOf(navigator.platform) >= 0;
   term = new Terminal({
     allowProposedApi: true,
+    overviewRuler: { width:14 },
     windowsPty: isWindows ? {
       // In a real scenario, these values should be verified on the backend
       backend: 'conpty',