Update and prepare for release 0.21.0 (#1529)

This PR updates and prepares for release 0.21.0

This PR is part of 1528

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

Author: yongtang

README.md

@@ -116,6 +116,7 @@ of releases [here](https://github.com/tensorflow/io/releases).
 
 | TensorFlow I/O Version | TensorFlow Compatibility | Release Date |
 | --- | --- | --- |
+| 0.21.0 | 2.6.x | Sep 12, 2021 |
 | 0.20.0 | 2.6.x | Aug 11, 2021 |
 | 0.19.1 | 2.5.x | Jul 25, 2021 |
 | 0.19.0 | 2.5.x | Jun 25, 2021 |

RELEASE.md

@@ -1,3 +1,18 @@
+# Release 0.21.0
+
+## Bug Fixes
+* Fix temporary file issue in s3
+* Remove extra build directory in python pip packages.
+
+## Thanks to our Contributors
+
+This release contains contributions from many people:
+
+Marcin Juszkiewicz, Mark Daoust, Vignesh Kothapalli, Yong Tang
+
+We are also grateful to all who filed issues or helped resolve them, asked and
+answered questions, and were part of inspiring discussions.
+
 # Release 0.20.0
 
 ## Major Features

tensorflow_io/python/ops/version_ops.py

@@ -14,5 +14,5 @@
 # ==============================================================================
 """version_ops"""
 
-version = "0.20.0"
+version = "0.21.0"
 require = "tensorflow>=2.6.0,<2.7.0"