Update README.md

Author: mbostock

README.md

@@ -4,10 +4,12 @@
 
 [**Observable Plot**](https://observablehq.com/plot/) is a free, [open-source](./LICENSE), JavaScript library for visualizing tabular data, focused on accelerating exploratory data analysis. It has a concise, memorable, yet expressive API, featuring [scales](https://observablehq.com/plot/features/scales) and [layered marks](https://observablehq.com/plot/features/marks) in the *grammar of graphics* style.
 
-<picture>
-  <source media="(prefers-color-scheme: dark)" srcset="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/plot/downloads-dark.svg">
-  <img alt="Daily downloads of Observable Plot" src="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/plot/downloads.svg">
-</picture>
+<a href="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/plot">
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/plot/downloads-dark.svg">
+    <img alt="Daily downloads of Observable Plot" src="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/plot/downloads.svg">
+  </picture>
+</a>
 
 <sub>Daily downloads of Observable Plot · [oss-analytics](https://observablehq.observablehq.cloud/oss-analytics/)</sub>