Implement baselineShift and verticalAlign (preferred).

Transverse Box Alignment, specifies how an inline-level box is aligned within the line, and by how much the box is shifted up from its alignment point.
 https://drafts.csswg.org/css-inline/#propdef-vertical-align
 https://www.w3.org/TR/css-inline-3/#propdef-baseline-shift
 https://www.w3.org/TR/css-inline-3/#transverse-alignment

lib/props.js

@@ -197,6 +197,29 @@ const lengthAdjust = PropTypes.oneOf(['spacing', 'spacingAndGlyphs']);
 */
 const textLength = PropTypes.string;
 
+/*
+ 2.2. Transverse Box Alignment: the vertical-align property
+
+ Name:	vertical-align
+ Value:	<‘baseline-shift’> || <‘alignment-baseline’>
+ Initial:	baseline
+ Applies to:	inline-level boxes
+ Inherited:	no
+ Percentages:	N/A
+ Media:	visual
+ Computed value:	as specified
+ Canonical order:	per grammar
+ Animation type:	discrete
+ This shorthand property specifies how an inline-level box is aligned within the line.
+ Values are the same as for its longhand properties, see below.
+
+ Authors should use this property (vertical-align) instead of its longhands.
+
+ https://www.w3.org/TR/css-inline-3/#transverse-alignment
+ https://drafts.csswg.org/css-inline/#propdef-vertical-align
+ */
+const verticalAlign = PropTypes.string;
+
 /*
  Name:	alignment-baseline
 
@@ -217,10 +240,32 @@ const textLength = PropTypes.string;
 */
 const alignmentBaseline = PropTypes.oneOf(['baseline', 'text-bottom', 'alphabetic', 'ideographic', 'middle', 'central', 'mathematical', 'text-top', 'bottom', 'center', 'top', 'text-before-edge', 'text-after-edge', 'before-edge', 'after-edge', 'hanging']);
 
+/*
+ 2.2.2. Alignment Shift: baseline-shift longhand
+
+ Name:	baseline-shift
+ Value:	<length> | <percentage> | sub | super
+ Initial:	0
+ Applies to:	inline-level boxes
+ Inherited:	no
+ Percentages:	refer to the used value of line-height
+ Media:	visual
+ Computed value:	absolute length, percentage, or keyword specified
+ Animation type:	discrete
+
+ This property specifies by how much the box is shifted up from its alignment point.
+ It does not apply when alignment-baseline is top or bottom.
+
+ https://www.w3.org/TR/css-inline-3/#propdef-baseline-shift
+*/
+const baselineShift = PropTypes.oneOfType([PropTypes.oneOf(['sub', 'super', 'baseline']), PropTypes.arrayOf(numberProp), PropTypes.string]);
+
 const textSpecificProps = {
     ...pathProps,
     ...fontProps,
     alignmentBaseline,
+    baselineShift,
+    verticalAlign,
     lengthAdjust,
     textLength,
 };