fix issue #20: add shortcut to open and to hide the menu

css/admin.css

@@ -23,3 +23,12 @@
 #side-menu-section select {
     margin: 10px 0 10px 0;
 }
+
+.keyboard-key {
+    padding: 1px 9px;
+    margin: 0 2px;
+    background: #eee;
+    border: 1px solid #aaa;
+    color: #555;
+    border-radius: 3px;
+}

css/sideMenu.css

@@ -80,7 +80,7 @@
     white-space: nowrap;
 }
 
-.side-menu-app a:hover, .side-menu-app.active a {
+.side-menu-app a:hover, .side-menu-app.active, .side-menu-app a:focus {
     background: var(--side-menu-current-app-background-color, #444);
 }