pass fontVariant to the axis label

closes #1821

Author: Fil

src/marks/axis.js

@@ -488,6 +488,7 @@ function labelOptions(
     fontFamily,
     fontSize,
     fontStyle,
+    fontVariant,
     fontWeight,
     monospace,
     pointerEvents,
@@ -508,6 +509,7 @@ function labelOptions(
     fontFamily,
     fontSize,
     fontStyle,
+    fontVariant,
     fontWeight,
     monospace,
     pointerEvents,

test/output/axisLabelFontVariant.svg

@@ -52,6 +52,12 @@ export async function axisLabelBothReverse() {
   });
 }
 
+export async function axisLabelFontVariant() {
+  return Plot.plot({
+    x: {domain: "abcde"},
+    marks: [Plot.axisX({label: "Letter", fontVariant: "small-caps"})]
+  });
+}
 export async function axisLabelVaryingFill() {
   return Plot.plot({
     x: {domain: "ABCDEF"},