Try: Add a scorecard

[StevenDufresne]

DO NOT MERGE.

We are currently printing test results in natural language to the respective action logs. In the future, it will make sense to share the theme results in a format that is easier to consume.

The Idea:

If we could create a scorecard, similar to lighthouse, we will be able to use that information to help authors and the theme directory.

This PR adds logic that prints error tests to a log called theme-scorecard.json in json format.

Example :

{
"title_check":0,
"page_should_return_200_status":0
}

It isn't very sophisticated at this point and only prints errors as a 0 score. It's a bit tricky because we currently only capture errors & warnings, and therefore the absence of a test result would suggest that it has passed. We could capture passes in the ui-check but I don't think that will work with the theme-check results.

[carolinan]

I think that before solving the problem with how to display positive results (scorecards/flags), there needs to be a discussion and decision about which checks to show results for.