Add hide scrollbars option

src/js/App.js

@@ -222,6 +222,9 @@ export class App extends React.Component {
     } else {
       className += ' notouch';
     }
+    if (this.props.hide_scrollbars) {
+      className += ' hide-scrollbars';
+    }
 
     return (
       <div className={className}>
@@ -368,6 +371,7 @@ export class App extends React.Component {
 const mapStateToProps = (state, ownProps) => ({
   theme: state.ui.theme,
   wide_scrollbar_enabled: state.ui.wide_scrollbar_enabled,
+  hide_scrollbars: state.ui.hide_scrollbars,
   smooth_scrolling_enabled: state.ui.smooth_scrolling_enabled,
   hotkeys_enabled: state.ui.hotkeys_enabled,
   allow_reporting: state.ui.allow_reporting,

src/js/views/Settings.js

@@ -280,6 +280,17 @@ class Settings extends React.Component {
                   Use wide scrollbars
                 </span>
               </label>
+              <label>
+                <input
+                  type="checkbox"
+                  name="hide_scrollbars"
+                  checked={ui.hide_scrollbars}
+                  onChange={(e) => uiActions.set({ hide_scrollbars: !ui.hide_scrollbars })}
+                />
+                <span className="label">
+                  Hide scrollbars
+                </span>
+              </label>
             </div>
           </div>