Dragscroll possible, scroll the screen with the mouse at desktop view

- click on a empty list area and drag the view left/right to scroll

client/components/boards/boardBody.jade

@@ -18,7 +18,7 @@ template(name="boardBody")
   else
     .board-wrapper(class=currentBoard.colorClass)
       +sidebar
-      .board-canvas.js-swimlanes(
+      .board-canvas.js-swimlanes.dragscroll(
         class="{{#if Sidebar.isOpen}}is-sibling-sidebar-open{{/if}}"
         class="{{#if MultiSelection.isActive}}is-multiselection-active{{/if}}"
         class="{{#if draggingActive.get}}is-dragging-active{{/if}}")

client/components/boards/boardBody.js

@@ -1,5 +1,6 @@
 import { ReactiveCache } from '/imports/reactiveCache';
 import { TAPi18n } from '/imports/i18n';
+import dragscroll from 'dragscroll';
 
 const subManager = new SubsManager();
 const { calculateIndex } = Utils;
@@ -219,6 +220,7 @@ BlazeComponent.extendComponent({
       boardComponent.openNewListForm();
     }
 
+    dragscroll.reset();
     Utils.setBackgroundImage();
   },