Bump backbone from 1.5.0 to 1.6.0

Bumps [backbone](https://github.com/jashkenas/backbone) from 1.5.0 to 1.6.0.
- [Commits](jashkenas/backbone@1.5.0...1.6.0)

---
updated-dependencies:
- dependency-name: backbone
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

package.json

@@ -60,7 +60,7 @@
     "webpack-cli": "~5.1.0"
   },
   "dependencies": {
-    "backbone": "1.5.0",
+    "backbone": "1.6.0",
     "bootstrap": "^3.3.7",
     "bootstrap-arrow-buttons": "^1.0.4",
     "jquery": "^3.2.1",