visited links color (#940)

fixes #935

Author: Fil

src/style.js

@@ -300,6 +300,7 @@ function applyHref(selection, href, target) {
     const h = href(i);
     if (h != null) {
       const a = document.createElementNS(namespaces.svg, "a");
+      a.setAttribute("fill", "inherit");
       a.setAttributeNS(namespaces.xlink, "href", h);
       if (target != null) a.setAttribute("target", target);
       this.parentNode.insertBefore(a, this).appendChild(this);

test/output/documentationLinks.svg

@@ -0,0 +1,11 @@
+import * as Plot from "@observablehq/plot";
+
+export default async function() {
+  return Plot.text({length: 1}, {
+    text: ["click me"],
+    x: 0,
+    y: 0,
+    fill: "red",
+    href: [`https://google.com/search?q=12345`]
+  }).plot();
+}

test/output/hrefFill.svg

@@ -90,6 +90,7 @@ export {default as hexbinText} from "./hexbin-text.js";
 export {default as hexbinZ} from "./hexbin-z.js";
 export {default as hexbinZNull} from "./hexbin-z-null.js";
 export {default as highCardinalityOrdinal} from "./high-cardinality-ordinal.js";
+export {default as hrefFill} from "./href-fill.js";
 export {default as identityScale} from "./identity-scale.js";
 export {default as integerInterval} from "./integer-interval.js";
 export {default as ibmTrading} from "./ibm-trading.js";