readme: add required python-jmespath for ansible json jmespath query

Some playbooks that use jmespath query like the matrix playbook while
getting changes for the "install irc-bridge registration" require the
python-jmespath package on client side to work, document this.

README.md

@@ -11,6 +11,7 @@ Install these packages:
   - terraform
   - terraform-provider-keycloak
   - python-typer
+  - python-jmespath
   - moreutils (for playbooks/tasks/reencrypt-vault-key.yml)
 
 ### Instructions