chore(ISD-783): Add badges (#10)

Author: Amanda H. L. de Andrade Katz

README.md

@@ -1,3 +1,6 @@
+[![CharmHub Badge](https://charmhub.io/synapse/badge.svg)](https://charmhub.io/synapse)
+[![Publish to edge](https://github.com/canonical/synapse-operator/actions/workflows/publish_charm.yaml/badge.svg)](https://github.com/canonical/synapse-operator/actions/workflows/publish_charm.yaml)
+[![Promote charm](https://github.com/canonical/synapse-operator/actions/workflows/promote_charm.yaml/badge.svg)](https://github.com/canonical/synapse-operator/actions/workflows/promote_charm.yaml)
 [![Discourse Status](https://img.shields.io/discourse/status?server=https%3A%2F%2Fdiscourse.charmhub.io&style=flat&label=CharmHub%20Discourse)](https://discourse.charmhub.io)
 
 # Synapse Operator