decomposed components with flipping transform have their path direction reversed, possibly causing dropouts if they overlap other components; this option ensures they will get reversed as they are decomposed (similar to what ufo2ft DecomposeComponentsFilter or Glyphs.app does when decomposing flipped components).
Also we allow specific instances of to set skipMissingComponents differently from the class default value, and add an alias to MissingComponentError so one doesn't need to import it explicitly but can the pen's class attribute.
In ufo2ft preProcessor, we need to know which specific glyphs were actually modified (converted to quadratic), in order to do other things while processing filters, not simply if the fonts were modified as a whole; thus, here I changed fonts_to_quadratic to return the set of modified glyph names instead of just True/False. The change is backward compatible because code that checks whether the returned value is True/False will continue to work since bool(set) is True for non-empty set, False for empty ones.
* Support sbix Glyphs with graphicType = "flip"
Since iOS 17.4 beta, Apple introduced the "flip" graphic type for the sbix glyphs to reference the another glyph to be flipped by their render engine. Their use case is for directional emojis.
Example emoji: https://emojipedia.org/woman_walking_facing_right#technical
This is the example of the output XML after this PR:
```
<glyph graphicType="flip" name="u1F3C3.0.M.u27A1" originOffsetX="0" originOffsetY="0">
<ref glyphname="u1F3C3.0.M" />
</glyph>
```
Before, it was just `<hexdata>` with some data in it.
technically we are tweaking the original example from the spec but it keeps the spirit, so that the product of glyph classes produces the same representation in the font as if the sequences were manually enumerated (while keeping the declaration order)
* Add optional transformRoundFunc to RoundingPen and RoundingPointPen
* Add tests
* Add doc about comparing UFO to TTF glyphs
* Use floatToFixedToFloat for example with rounding
