[Details] Add tab listing (non-)uniform glyph sets

[felipesanches]

Originally submitted at fonttools/fontbakery#1233

@davelab6 reported: "There's a high priority set of work to fix fonts in families to be uniform glyph sets across the collection... so, a 2nd step after fonttools/fontbakery#1232 is to make something similar to the Missing Codepoints spreadsheet in the dashboard so we can burn down progress against that check. "