Bump sortablejs from 1.12.0 to 1.13.0

Bumps [sortablejs](https://github.com/SortableJS/Sortable) from 1.12.0 to 1.13.0.
- [Release notes](https://github.com/SortableJS/Sortable/releases)
- [Commits](https://github.com/SortableJS/Sortable/commits/1.13.0)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -15,7 +15,7 @@
     "jstree": "^3.3.11",
     "opensans-webkit": "^1.1.0",
     "popper.js": "^1.16.1",
-    "sortablejs": "^1.12.0",
+    "sortablejs": "^1.13.0",
     "underscore": "^1.12.0",
     "vis": "^4.21.0",
     "webpack-merge": "^5.7.3"