[notodiff]: Add heuristics to minimize false diff reporting

[marekjez86]

Notodiff works well for different versions of the same font. However, sometimes it is useful to compare similar fonts of different vendors.

Despite their glyph coverage can be very close, notodiff finds and reports lots of differences, because glyph names assignment is not standardized and font vendors can assign completely different names for glyphs that look identical and mapped to the same unicode characters.

Though strict mapping is impossible, provide some heuristics that can map some of glyph names and reduce number of reported false differences.

Examples:
Rule-based names: ‘glyphXXXX’ to ‘uniXXXX‘
Cmap reverse mapping ‘glyphXXXX’ (font 1 cmap) -> code point XXXX -> (font 2 cmap) ‘uniXXXX’