docs: Add GCE install guide to install README
Add the new Google Compute Engine installation guide to the
installation README, reworking this doc to add in a table of contents
and a new "Cloud services" section.
Fixes
# Kata Containers installation user guides
+* [Prerequisites](#prerequisites)
+* [Installing Kata Containers](#installing-kata-containers)
+ * [Distros](#distros)
+ * [Cloud services](#cloud-services)
+* [Further information](#further-information)
+
+## Prerequisites
+
Kata Containers requires nested virtualization or bare metal.
-See the [hardware requirements](https://github.com/kata-containers/runtime/blob/master/README.md#hardware-requirements) to see if your system is capable of running Kata Containers.
+See the
+[hardware requirements](https://github.com/kata-containers/runtime/blob/master/README.md#hardware-requirements)
+to see if your system is capable of running Kata Containers.
+
+## Installing Kata Containers
-Select your preferred distribution:
+Select your preferred distribution or cloud service:
+
+### Distros
* [CentOS](centos-installation-guide.md)
* [Fedora](fedora-installation-guide.md)
* [Red Hat](rhel-installation-guide.md)
* [Ubuntu](ubuntu-installation-guide.md)
-For further information, see:
+### Cloud services
+
+* [Google Compute Engine (GCE)](gce-installation-guide.md)
+
+## Further information
* The [the upgrading document](../Upgrading.md).
* The [developer guide](../Developer-Guide.md).
