Full release of actions/core 1.6.0 with oidc behavior (#919)

* OIDC Client for actions/core

Co-authored-by: Sourav Chanduka <souravchanduka37@gmail.com>
Co-authored-by: Sourav Chanduka <souravchanduka@users.noreply.github.com>
Co-authored-by: Tingluo Huang <tingluohuang@github.com>

RELEASES.md

@@ -1,5 +1,9 @@
 # @actions/core Releases
 
+### 1.6.0
+- [Added OIDC Client function `getIDToken`](https://github.com/actions/toolkit/pull/919)
+- [Added `file` parameter to `AnnotationProperties`](https://github.com/actions/toolkit/pull/896) 
+
 ### 1.5.0
 - [Added support for notice annotations and more annotation fields](https://github.com/actions/toolkit/pull/855)