Coldtype

Added
- `Easeable.ec` as easing-cumulative (to help with partial rotations,
as in the new truchet animation examples, and examples/animations/ec.py)

Added
- `P.spread` as horizontal-only counterpart to `P.stack` (paired with `P.track` and `P.lead` respectively, funny that they rhyme oppositely whoops)
Fixed
- Default `"."` in ALL_FONT_DIRS for linux (so colab notebooks search in their uploaded files by default)

Added
- `Runon.attach`
Fixed
- Explicit include of ufoLib2 for blender

Fixed
- `glyph_to_uni` in packaged mode

Added
- New arg `round_result` on `SkiaImage.align`, to fix jaggy image aligning; defaults to True but is disableable

Added
- New transparency background when `bg` not specified
- `render_bg` now defaults to `True`, since that seems to be the most common use-case
- `ufo2ft` in `[blender]` optional requirements
- simple `gifski` wrapper importable from `coldtyper.renderable.animation`
Fixed
- Better error message when trying to "release" via ffmpeg but no files have been rendered