Add WebPageTest link when too big

[tunetheweb]

At the moment when the test results are too big for the comment we add this:

Webpage test results that are too big for a comment are available as the action's artifact.

Example: https://github.com/HTTPArchive/custom-metrics/pull/145#issuecomment-2365230655

It would be nice if we also got a WebPageTest link so we can see them there too. Is this possible @max-ostapenko ?