Prepare 8.0.0 changelog

Author: davidweterings

CHANGES

@@ -1,3 +1,12 @@
+8.0.0 (2020-04-28)
+------------------
+Regenerated Commercetools types (needed missing Discount state enums).
+The 'LoggedResource' no longer exists, so a lot of types got changed,
+but effectively still have the same attributes.
+For safety we're doing a major release.
+
+- Testing: add support for updating product type sets in mock server
+
 7.0.0 (20202-04-16)
 -------------------
 Note this release has some breaking changes regarding optional typing. If