Add “decompose” attributes to GlyphData.xml

[delucis]

Glyphs supports a decompose attribute on <glyph> elements in GlyphData.xml:

decompose defines the components of a compound glyph. In other words, the parts that make up the glyph. This information is used when you construct such a letter using the Glyph > Make Component Glyph command (cmd + opt + shift + C).

Make sure the base letter comes first and all the diacritics follow. This is also useful for ligatures. In that case, you add the names of the glyphs that comprise the ligature, e.g. decompose="f, f, k" for an f_f_k ligature.

Among the various supported attributes not currently included in GlyphData.xml, decompose is probably the most useful, but the required data may need to be collected manually.

[delucis]

At least some of the data may be retrievable from the ligatures section of Bravura’s metdata.