add downloads to README

Author: mbostock

README.md

@@ -2,6 +2,14 @@
 
 [**Observable Framework**](https://observablehq.com/framework/) is a free, [open-source](./LICENSE), static site generator for data apps, dashboards, reports, and more. Framework combines JavaScript on the front-end for interactive graphics with any language on the back-end for data analysis. Framework features [data loaders](https://observablehq.com/framework/loaders) that precompute static snapshots of data at build time for dashboards that load instantly.
 
+<figure>
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/framework/downloads-dark.svg">
+    <img alt="Daily downloads of Observable Framework" src="https://observablehq.observablehq.cloud/oss-analytics/@observablehq/framework/downloads.svg">
+  </picture>
+  <figcaption>Daily downloads of Observable Framework</figcaption>
+</figure>
+
 ## Documentation 📚
 
 https://observablehq.com/framework/