* Improve MathML for classes
* Fix lint errors
* Fix another lint error
* Simplify MathML resulting from single character box
* Fix lint errors
* make some of the arrays in our html/mathml helper functions readonly
* simplify comibining chars
* try combining chars in text operators instead of all ordgroups
* ensure that adjacent chars have the same classes
* fix phantom tests
* extract canCombe from tryCombineChars, check for skew and maxFontSize
* check prev.italic !== next.italic
* use the last character's italic correction.
* Make MathNodeClass include documentFragment for ergonomics.
* Separate out the HTML and MathML documentFragments.
These two documentFragments have different additional properties/methodsi
and limitations. This separation is needed for porting buildMathML to
flow.
* Coalesce the documentFragment subclasses to avoid subclassing polyfill.
* Make DomSpan and SvgSpan type aliases again instead of subclasses.
* Remove type MathNodeClass in favor of MathDomNode.
* Resolve $FlowFixMes by reordering variants of a union type.