need yaml validation to help with feedback

[SteveLasker]

example1: version is missing :

version 1.0.0
steps:
    - cmd: docker.io/hello-world

example2: cmd wasn't preceded with -, version doesn't use v1.0.0

version: 1.0.0
steps:
    cmd: docker.io/hello-world

Expectation:
provide the line number of the invalid yaml
provide hints, such as
Supported versions include v1.0.0, v.1.0.1, ... Note Task versions start with v
line 3 cmd not recognized. each step must begin with -