Added 1.2.0 release notes (#1056)

* Added 1.2.0 release notes

* typos

Author: mhowlett

CHANGELOG.md

@@ -1,3 +1,16 @@
+# 1.2.0
+
+## Enhancements
+
+- References librdkafka v1.2.0. Refer to the [release notes](https://github.com/edenhill/librdkafka/releases/tag/v1.2.0) for more information. Headline feature is consumer side support for transactions.
+- Added `IDictionary` overload to `Config` constructors (contribution by @AndyPook).
+- `Confluent.Kafka`, `Confluent.SchemaRegistry` and `Confluent.SchemaRegistry.Serdes` are now all signed, and `Confluent.Kafka.StrongName` depreciated.
+
+## Fixes
+
+- Updated the librdkafka build load order so that the most featureful version is used on any given platform.
+
+
 # 1.1.0
 
 ## Enhancements