Add an example for Azure Function invocations

[JohannesRudolph]

meshStack support invoking azure cloud functions as part of landing zones. We do have an example for how to give the replicator SPN the required permissions in https://github.com/meshcloud/terraform-azure-meshplatform/tree/main/examples/azure-integration-with-additional-resource-access but do not have an example how to deploy such a function.

However, this is a rarely used feature and we see much more usage of building-blocks for scenarios that were solved by functions invocations before, so I'm just putting this here for completeness but don't expect that we will close this gap soon.