Update RELEASE.md

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

RELEASE.md

@@ -1,3 +1,27 @@
+# Release 0.8.0
+
+## Major Features
+* `tensorflow_io.json`: JSON Dataset support.
+* `tensorflow_io.dicom`: Medical image DICOM format support.
+* `tensorflow_io.genome`: DNA Sequence FastQ format support added.
+* `tensorflow_io.ffmpeg`: FFmpeg now support selection of video, audio,
+  and subtitle sub streams.
+* `tensorflow_io.ffmpeg`: FFmpeg now support decode video from memory.
+* `tensorflow_io.kafka`: Kafka Dataset now support Kafka Schema Registry.
+* `tensorflow_io.audio`: WAV format now support 24 bit audio streams.
+* `tensorflow_io.text`: Regex capture group (re2_full_match) support.
+
+## Thanks to our Contributors
+
+This release contains contributions from many people:
+
+Aleksey Vlasenko, Bryan Cutler, Damien Pontifex, Duke Wang, Jiacheng Xu,
+Marcelo Lerendegui, Mark Daoust, Ouwen Huang, Suyash Kumar, Yong Tang,
+Yuan Tang, android
+
+We are also grateful to all who filed issues or helped resolve them, asked and
+answered questions, and were part of inspiring discussions.
+
 # Release 0.7.0
 
 ## Major Features