Document/provide example of conditional tasks (if)

[mjnagel]

Maru currently supports if logic for tasks, but I don't think there are any docs explaining this functionality or providing an example.

An example and docs would be helpful to bring attention to this feature.

[Racer159]

Putting this here for now - its a test but is at least a breadcrumb: https://github.com/defenseunicorns/maru-runner/blob/main/src/test/tasks/loop-task.yaml#L18

[mjnagel]

This one also has some more examples of the conditional behavior: https://github.com/defenseunicorns/maru-runner/blob/main/src/test/tasks/conditionals/tasks.yaml

Even just linking to those would be a good start in docs.