Template expressions cause syntax errors in YAML files

When using the Azure Pipelines extension against a YAML file containing a template expression it reports errors when the file is valid.

steps:
 - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
    - powershell: echo "Hello"

Reports on the ${{ line: unexpected property, The first property must be a script.

[vtbassmatt]

We’re looking into when we can fund it. Now that template parameters and other template-using features have gathered some steam, the current behavior is becoming less and less defensible.

[s-bauer]

Supporting this is really important in my eyes! Please put this in a high priority bucket!