Add release notes

Author: papandreou

documentation/releases.md

@@ -12,6 +12,13 @@ Here is a very high level overview of the major releases. See the
 [changelog](https://github.com/unexpectedjs/unexpected/blob/master/CHANGELOG.md)
 for more details.
 
+### v13.0.0 (2022-04-26)
+
+- Drop support for node.js < 14
+- Add support for assertions on `Set` instances, [documentation](../assertions/Set/) ([#783](https://github.com/unexpectedjs/unexpected/pull/783))
+- Remove legacy support for addAssertion without a subject type ([782](https://github.com/unexpectedjs/unexpected/pull/782))
+- Add the parent expect to the prototype chain of a child expect ([785](https://github.com/unexpectedjs/unexpected/pull/785))
+
 ### v12.0.0 (2020-11-18)
 
 - Drop support for node.js < 10