Add release date for v0.19.8

Viktor Lövgren · Viktor Lövgren · commit 2898c7056098 · 2019-04-02T09:53:58.000+01:00
diff --git a/notes/0.19.8.markdown b/notes/0.19.8.markdown
@@ -16,3 +16,5 @@
 [#112]: https://github.com/ovotech/fs2-kafka/pull/112
 [#113]: https://github.com/ovotech/fs2-kafka/pull/113
 [#114]: https://github.com/ovotech/fs2-kafka/pull/114
+
+Released on 2019-04-02.
