Vfblib

* Workaround for certain float values with 16 decimals being written incorrectly by ufonormalizer (thanks boldmonday and justvanrossum)
* Bugfix for VFBs with empty OpenType feature code
* Update dependencies

- Use `public.groupOrder` UFO lib key (https://github.com/unified-font-object/ufo-spec/issues/216)
- Implement handling TrueType stems which are rounded to 1 pixel starting at higher ppms than 0
- Improve typing annotations and checks
- Avoid a traceback when there is a hint mask but no hint in a glyph
- Update dependencies
- Drop support for Python 3.8

- Fix handling unusual alignment values in TTH

- "Unoptimize" another closepath situation

- Preserve explicit last line instead of closepath in contours
- Store composite transformation values as integer if possible

Changes in UFO output:

- Support sidebearing hints in composites
- Remove excessive blank lines in feature code
- Convert group names in FL-generated kern feature to standard UFO names
- Fix "minimal" converter logic
- Re-add missing fontNote font info entry
- Add `vfb3ufo` command line option `-k`/`--add-kerning-groups` to add kerning group definitions to feature code