Convert README to markdown

Convert the README file from reST to markdown
as the GitHub support for reST is poor and it's
more consistent with the charms to have a
README in markdown.

The CDG is being changed in the same way:
https://review.opendev.org/c/openstack/charm-deployment-guide/+/782607

Change-Id: I69584c645432615e2a637e160b1b4a82b4b6205f

README.md

@@ -0,0 +1,38 @@
+# OpenStack Charm Guide
+
+[![tags][image-badge-cg]][image-link-openstack-tags]
+
+The [OpenStack Charm Guide][cg] is the main source of information for the
+development of the [OpenStack Charms][openstack-charms]. Release notes and
+support notes are also to be found here.
+
+## Building
+
+To build the guide run this simple command:
+
+    tox
+
+The resulting HTML files will be found in the `doc/build/html` directory. These
+can be opened individually with a web browser or hosted by a local web server.
+
+## Contributing
+
+Documentation issues can be filed on [Launchpad][lp-bugs-cg].
+
+This repository is under version control and is managed via the [OpenStack
+Gerrit system][gerrit-openstack] (see the [OpenDev Developer’s
+Guide][opendev-dev-guide]). For specific guidance on working with the
+documentation hosted on [docs.openstack.org][link] please read the [OpenStack
+Documentation Contributor Guide][openstack-doc-guide].
+
+<!-- LINKS -->
+
+[image-badge-cg]: https://governance.openstack.org/tc/badges/charm-guide.svg
+[image-link-openstack-tags]: http://governance.openstack.org/tc/reference/tags/index.html
+[cg]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide
+[openstack-charms]: https://launchpad.net/openstack-charms
+[lp-bugs-cg]: https://bugs.launchpad.net/charm-guide/+filebug
+[gerrit-openstack]: https://review.openstack.org
+[opendev-dev-guide]: https://docs.openstack.org/infra/manual/developers.html
+[openstack-doc-guide]: https://docs.openstack.org/doc-contrib-guide/index.html
+[link]: https://docs.openstack.org

README.rst

@@ -1,19 +0,0 @@
-========================
-Team and repository tags
-========================
-
-.. image:: https://governance.openstack.org/tc/badges/charm-guide.svg
-    :target: https://governance.openstack.org/tc/reference/tags/index.html
-
-.. Change things from this point on
-
-=====================
-OpenStack Charm Guide
-=====================
-To build the guide, execute the following command::
-
-  $ tox
-
-After running ``tox``, the documentation will be available for viewing
-in HTML format in the ``doc/build/`` directory. View these new documents
-in your favorite web browser.

setup.cfg

@@ -2,7 +2,7 @@
 name = charm-guide
 summary = OpenStack Charm Guide
 description-file =
-    README.rst
+    README.md
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/charm-guide/latest/