update CHANGELOG.md

Author: ircwaves

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Some mishandled cases for datetime intervals [#363](https://github.com/stac-utils/pystac-client/pull/363)
 - Collection requests when the Client's url ends in a '/' [#373](https://github.com/stac-utils/pystac-client/pull/373), [#405](https://github.com/stac-utils/pystac-client/pull/405)
 - Parse datetimes more strictly [#364](https://github.com/stac-utils/pystac-client/pull/364)
+- Fix parse fail when header has multiple '=' characters
 
 ### Removed