Highlight production bundles in bold in the Danger integration comment

[gaearon]

We added integration with Danger in #11865.
It shows a bundle size difference on PRs, like this: #12028 (comment).

We should change the output so that production bundles are bold in the results. I think we can also remove the red triangle on increase from the development bundles because they're not as important.

[clairecliu]

i would like to give this a try

[gaearon]

You got it!

[gaearon]

Fixed in #12054.