Display of data that is "almost equal" between rows #394

• For numbers: e.g. 100.001, 100.002, 100.003, Feature Request: pillar.round = FALSE #97 (comment)
• For strings: e.g. "abcde", "abcdf", "abdfe", Feature Request: pillar.round = FALSE #97 (comment), Show as many characters as necessary for a string column #101

Should we implement a class that applies subtle styling to the parts of strings/numbers that are the same across all columns, and that sets the minimum width accordingly? Should we even move common information to the header?