bump Changelog.md

Author: yvovandoorn

CHANGELOG.md

@@ -1,3 +1,10 @@
+## v5.15.0
+* `management.Guardian`: Fixed minor bug when unmarshalling Policy string array ([#211](https://github.com/go-auth0/auth0/pull/211))
+
+NOTES:
+
+* Added support for .env config file support ([#210](https://github.com/go-auth0/auth0/pull/210))
+
 ## v5.14.1
 * `management.Connection`: Add support for Auth0 SAML connection entityId option ([#209](https://github.com/go-auth0/auth0/pull/209))