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/attributes.js

@@ -112,6 +112,8 @@ const PathAttributes = {
 const TextSpecificAttributes = {
     ...RenderableAttributes,
     alignmentBaseline: true,
+    baselineShift: true,
+    verticalAlign: true,
     lengthAdjust: true,
     textLength: true,
 };