FontFeature.oldstyleFigures constructor
Use oldstyle figures.
Some fonts have variants of the figures (e.g. the digit 9) that, when this feature is enabled, render with descenders under the baseline instead of being entirely above the baseline.
This overrides FontFeature.slashedZero.
See also:
Implementation
const FontFeature.oldstyleFigures() : feature = 'onum', value = 1;