re-enable ?intent=fork

This reverts commit 402c2a5.

Author: mbostock

docs/.vitepress/markdown-it-plot.ts

@@ -26,7 +26,7 @@ export default function plot(md) {
           directives.includes("hidden")
             ? `<div style="display: none;">\n`
             : href
-            ? `<a class="plot-fork" href="${md.utils.escapeHtml(href)}" target="_blank" title="Open on Observable">Fork</a>`
+            ? `<a class="plot-fork" href="${md.utils.escapeHtml(href)}?intent=fork" target="_blank" title="Open on Observable">Fork</a>`
             : ""
         }`;
         if (/^Plot\.plot\(/.test(content)) {

docs/features/markers.md

@@ -26,7 +26,7 @@ A **marker** defines a graphic drawn on vertices of a [line](../marks/line.md) o
   </label>
 </p>
 
-:::plot https://observablehq.com/d/cfc5b4e46aa18b57
+:::plot https://observablehq.com/d/cfc5b4e46aa18b57?intent=fork
 ```js-vue
 Plot.plot({
   marks: [