link contours example

docs/d3-contour.md

@@ -8,19 +8,22 @@ import PlotRender from "./components/PlotRender.js";
 
 # d3-contour
 
-<PlotRender :options='{
-  axis: null,
-  aspectRatio: 1,
-  marks: [
-    Plot.contour(volcano.values, {
-      width: volcano.width,
-      height: volcano.height,
-      fill: Plot.identity,
-      stroke: "black",
-      interval: 5
-    })
-  ]
-}' />
+<div style="margin: 1em 0;">
+  <PlotRender :options='{
+    axis: null,
+    aspectRatio: 1,
+    marks: [
+      Plot.contour(volcano.values, {
+        width: volcano.width,
+        height: volcano.height,
+        fill: Plot.identity,
+        stroke: "black",
+        interval: 5
+      })
+    ]
+  }' />
+  <a href="https://observablehq.com/@d3/volcano-contours/2?intent=fork" style="font-size: smaller;" target="_blank">Fork ↗︎</a>
+</div>
 
 This module computes contour polygons by applying [marching squares](https://en.wikipedia.org/wiki/Marching_squares) to a rectangular grid of numeric values. For example, the contours above show the topography of [Maungawhau](https://en.wikipedia.org/wiki/Maungawhau_/_Mount_Eden).