Bump bootstrap-select from 1.12.4 to 1.13.6

Bumps [bootstrap-select](https://github.com/snapappointments/bootstrap-select) from 1.12.4 to 1.13.6.
- [Release notes](https://github.com/snapappointments/bootstrap-select/releases)
- [Changelog](https://github.com/snapappointments/bootstrap-select/blob/v1.13.0-dev/CHANGELOG.md)
- [Commits](snapappointments/bootstrap-select@v1.12.4...v1.13.6)

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

package.json

@@ -20,7 +20,7 @@
         "blueimp-tmpl": "^2.5.7",
         "bootstrap-2.3.2": "^1.0.0",
         "bootstrap-datepicker": "^1.9.0",
-        "bootstrap-select": "1.12.4",
+        "bootstrap-select": "1.13.6",
         "bootstrap-switch": "^3.4.0",
         "d3": "^3.5.17",
         "jquery": "1.12.4",