Bump js-yaml from 3.12.0 to 3.13.1 in /webapp (#48)

Bumps [js-yaml](https://github.com/nodeca/js-yaml) from 3.12.0 to 3.13.1.
- [Release notes](https://github.com/nodeca/js-yaml/releases)
- [Changelog](https://github.com/nodeca/js-yaml/blob/master/CHANGELOG.md)
- [Commits](https://github.com/nodeca/js-yaml/compare/3.12.0...3.13.1)

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

webapp/package-lock.json

@@ -4261,9 +4261,9 @@
       "integrity": "sha1-mGbfOVECEw449/mWvOtlRDIJwls="
     },
     "js-yaml": {
-      "version": "3.12.0",
-      "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-3.12.0.tgz",
-      "integrity": "sha512-PIt2cnwmPfL4hKNwqeiuz4bKfnzHTBv6HyVgjahA6mPLwPDzjDWrplJBMjHUFxku/N3FlmrbyPclad+I+4mJ3A==",
+      "version": "3.13.1",
+      "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-3.13.1.tgz",
+      "integrity": "sha512-YfbcO7jXDdyj0DGxYVSlSeQNHbD7XPWvrVWeVUujrQEoZzWJIRrCPoyk6kL6IAjAG2IolMK4T0hNUe0HOUs5Jw==",
       "dev": true,
       "requires": {
         "argparse": "^1.0.7",