add interrupt kernel command to default items

Author: ciusji

packages/cell-toolbar/src/celltoolbartracker.ts

@@ -337,6 +337,10 @@ const defaultToolbarItems: ToolbarRegistry.IWidget[] = [
     command: 'notebook:run-cell',
     name: 'run-cell'
   },
+  {
+    command: 'notebook:interrupt-kernel',
+    name: 'interrupt'
+  },
   {
     command: 'notebook:duplicate-below',
     name: 'duplicate-cell'