font-variant accepts the values in the grammar
https://drafts.csswg.org/css-fonts-4/#propdef-font-variant

```
normal | none | [ <common-lig-values> || <discretionary-lig-values> ||
<historical-lig-values> || <contextual-alt-values> ||
[ small-caps | all-small-caps | petite-caps | all-petite-caps |
  unicase | titling-caps ] ||
[ stylistic(<feature-value-name>) || historical-forms ||
  styleset(<feature-value-name>#) ||
  character-variant(<feature-value-name>#) ||
  swash(<feature-value-name>) ||
  ornaments(<feature-value-name>) ||
  annotation(<feature-value-name>) ] ||
<numeric-figure-values> ||<numeric-spacing-values> ||
<numeric-fraction-values> || ordinal || slashed-zero ||
<east-asian-variant-values> || <east-asian-width-values> ||
ruby || [ sub | super ] ]
```

font-variant serializes using canonical order.