Bump js-yaml in /examples/fork-ts-checker-webpack-plugin (#946)

Bumps [js-yaml](https://github.com/nodeca/js-yaml) from 3.12.1 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](nodeca/js-yaml@3.12.1...3.13.1)

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

examples/fork-ts-checker-webpack-plugin/yarn.lock

@@ -2293,9 +2293,9 @@ js-tokens@^3.0.2:
   integrity sha1-mGbfOVECEw449/mWvOtlRDIJwls=
 
 js-yaml@^3.7.0:
-  version "3.12.1"
-  resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.12.1.tgz#295c8632a18a23e054cf5c9d3cecafe678167600"
-  integrity sha512-um46hB9wNOKlwkHgiuyEVAybXBjwFUV0Z/RaHJblRd9DXltue9FTYvzCr9ErQrK9Adz5MU4gHWVaNUfdmrC8qA==
+  version "3.13.1"
+  resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.13.1.tgz#aff151b30bfdfa8e49e05da22e7415e9dfa37847"
+  integrity sha512-YfbcO7jXDdyj0DGxYVSlSeQNHbD7XPWvrVWeVUujrQEoZzWJIRrCPoyk6kL6IAjAG2IolMK4T0hNUe0HOUs5Jw==
   dependencies:
     argparse "^1.0.7"
     esprima "^4.0.0"