Use built-in 'cw-block' class to apply negative margin so that drag handle for...

Use built-in 'cw-block' class to apply negative margin so that drag handle for courseware block appears in the right place

courseware-block/src/courseware-excalidraw-block.vue

 <template>
-    <div class="cw-excalidraw-block">
+    <div class="cw-excalidraw-block cw-block">
         <component
             :is="coursewarePluginComponents.CoursewareDefaultBlock"
             ref="defaultBlock"