Add release documentation for SIG Addons (#116)

* Add release documentation for SIG Addons

* Fix grammar in release doc

Author: seanpmorgan

sigs/addons/RELEASE.md

@@ -0,0 +1,21 @@
+# SIG Addons Releases
+
+SIG Addons release process consists of the folowing steps:
+1. Create new rX.X branch on tensorflow/addons
+2. Create and merge a new PR into the release branch
+	* Set the correct version and suffix in [version.py](https://github.com/tensorflow/addons/blob/master/tensorflow_addons/version.py)
+	* Freeze the tensorflow version in [requirements.txt](https://github.com/tensorflow/addons/blob/master/requirements.txt)
+	* Remove `--nightly` flag from [release scripts](https://github.com/tensorflow/addons/tree/master/tools/ci_build/builds)
+	* Compile the docs: [instructions](https://github.com/tensorflow/addons/tree/master/tools/docs)
+3. Trigger [Travis build](https://travis-ci.org/tensorflow/addons)
+    * This will test and build linux+macos wheels and publish to PyPi
+4. Publish and tag a [release on Github](https://github.com/tensorflow/addons/releases)
+    * Add updates for new features, enhancements, bug fixes
+    * Add contributors using `git shortlog <last-version>..HEAD -s`
+
+
+## SIG Addons Release Team
+
+Current Release Team:
+- Sean Morgan - GitHub: [@seanpmorgan](https://github.com/seanpmorgan) - PyPI: [seanmorgan](https://pypi.org/user/seanmorgan/)
+- Yan Facai(颜发才) - GitHub: [@facaiy](https://github.com/facaiy) - PyPI: [facaiy](https://pypi.org/user/facaiy/)