Minor tweaks

chore: ignore swap files

Fix box-overwrapping bug

Support transition between horizontal/vertical mode

Draw boxes with thick lines instread of rects

Bump to 0.7.2

Support transition between symbols

Add boxplot.symbol() to change data point symbols

- `boxplotSymbolCircle` renders conventional small dots
- `boxplotSymbolTick` renders thin lines instead of dots
- Bump version to 0.7.0

Bump version to v0.6.4