Add a way to include 'non-compared' columns

[tmtmtmtm]

If we're only comparing a very small number of columns — perhaps even only one — and the values are only IDs (and might be missing in some cases), then the resulting output can be quite baffling, and largely unusable: e.g. https://www.wikidata.org/w/index.php?title=Wikidata:WikiProject_every_politician/Italy/Deputies/prompts/OpenPolis/comparison&oldid=609580809

This would be a lot more readable if we could include, say, a name field, but doing so would create lots of extra rows of diffs where those names aren't the same in each source. Ideally we'd like a way to say "We don't care if the name is different, but we would like the name field included for any row where the ID field differs"