feat(synapse): add deployment type podman

roles/synapse/README.md

@@ -18,12 +18,12 @@ The following variables need to be populated:
 
 ## Deployment methods
 
-### Docker
+- `docker`
+- `podman`
 
-Set `synapse_deployment_method: docker` to deploy synapse in docker container(s).
-This is currently the default.
+Set `synapse_deployment_method` to one of the supported deployment methods.
+The current default is `docker`.
 
-### Planned methods
+### Planned deployment methods
 
-- virtual env + systemd
-- podman
+- `venv` - Python virtual env supervised with `systemd`