Add metrics JSON to .gitignore?

[joeflack4]

Overview

We have these metadata/*-metrics.json files, but they have the same information, from what I can tell, as the docs/metrics/*.md files that we generate from them. It feels redundant to commit both. Advantage of removing them would be that build diffs would decrease.

There might be some additional things in the JSON that aren't in the .md files, but I wonder if that's still enough reason to keep them. That stuff could also potentially be rendered in the .md.