informational rules in plan policies.

Rules are currently evaluated on warn or deny, however in some scenarios its nice to give the user informational messages.
Specifically thinking of the Self-Service approach through blueprints, this is really handy for our users who aren’t familiar with IaC and code, however as it skips the PR element the benefits of infracost are somewhat diluted.
It would be great to have an informational rule that runs each time to provide the end user the updated cost of the resources deployed by the stack. I’m sure there will be other scenarios where an informational update in the stack would be useful.