Add a changelog entry

Author: RKushnir

CHANGELOG.md

@@ -1,3 +1,14 @@
+Unreleased
+------
+#### Enhancements
+- Print warnings about incorrectly used ignore-markers (#325), such as start-marker
+without a corresponding stop-marker, or two start-markers without a stop-marker in-between etc.
+
+0.18.1
+------
+#### Changes
+- Use explicit steps to remove 1.16 deprecation warning in Cobertura (#322).
+
 0.18.0
 ------
 #### Changes