Fix README file

change format to .rst

At this moment look not good:
https://opendev.org/openstack/etcd3gw/src/branch/master/README.md

Change-Id: If14af67bb557b7c219ca37af95da69565779e04f
Signed-off-by: Ivan Anfimov <lazekteam@gmail.com>

README.rst

@@ -1,16 +1,9 @@
-========================
-Team and repository tags
-========================
-
-.. image:: https://governance.openstack.org/tc/badges/oslo.config.svg
-    :target: https://governance.openstack.org/tc/reference/tags/index.html
-
-.. Change things from this point on
-
 ===========================
 etcd3 gateway Python Client
 ===========================
 
+.. image:: https://governance.openstack.org/tc/badges/etcd3gw.svg
+
 .. image:: https://img.shields.io/pypi/v/etcd3gw.svg
      :target: https://pypi.org/project/etcd3gw/
      :alt: Latest version
@@ -25,4 +18,4 @@ The etcd3gw library provides a python client for etcd3 grpc-gateway v3 API.
 * Documentation: https://docs.openstack.org/etcd3gw/latest/
 * Source: https://opendev.org/openstack/etcd3gw/
 * Bugs: https://bugs.launchpad.net/python-etcd3gw
-* Release notes:  https://docs.openstack.org/releasenotes/etcd3gw/
+* Release notes: https://docs.openstack.org/releasenotes/etcd3gw/