Added release notes for C++ (#714)

Author: RickWinter

sdk/core/azure-core/CHANGELOG.md

@@ -1,9 +1,23 @@
 # Release History
 
-## 1.0.0-beta.2 (Unreleased)
+## 1.0.0-beta.2 (2020-10-09)
 
+### Breaking Changes
+
+- Throw Azure::Http::TransportException if creating new connection fails.
+- Response objects store Nullable\<T\>.
+
+### Bug Fixes
+
+- Switched to a more stable wait on sockets to address connection timeouts.
+- Replace `Nullable(const T&)` with `Nullable(T)` to avoid extra copy when initialized with an rvalue.
+
+### Other changes and Improvements
+
+- Improved performance on windows when using libcurl.
+- Pinned the version of package dependencies.
+- Added NOTICE.txt for 3rd party dependencies.
 
 ## 1.0.0-beta.1 (2020-09-09)
 
 - Initial release
-