Readme updates in prep for release (open-telemetry#2623)

Author: cijothomas

README.md

@@ -35,6 +35,10 @@ of telemetry is intentionally left to other tools.
 
 *[Supported Rust Versions](#supported-rust-versions)*
 
+## Release Notes
+
+You can find the release notes (changelog) [here](./CHANGELOG.md).
+
 ## Supported Rust Versions
 
 OpenTelemetry is built against the latest stable release. The minimum supported