From HTML sampler, attributed to Karl Pentzlin. Covers many digraphs and
trigraphs, some of which have been replaced by presentational forms if
available in Unicode. This is mostly a technical test of code points,
not of proper typesetting: proper ligatures should be determined by fonts
and rarely matches only these 6 sets.
Common Fraktur ligatures: ch ck ff ffi ffl fft fi fl ft ll ſch ſi ſſ ſt tz;
replaced by single glyphs for: ff ffi ffl fi fl ſt.
Usage of long s precludes inclusion of U+FB06 st, but this is already present
elsewhere.