Updated API Reference Link in README.md (d3#3562)

aedmondson · web-flow · commit 778af6bc945e · 2022-03-28T17:49:12.000-07:00
The API Reference link at the top of README.md used "master" instead of "main". GitHub would redirect to the correct page, but with a warning message.
diff --git a/README.md b/README.md
@@ -7,7 +7,7 @@
 ## Resources
 
 * [Introduction](https://observablehq.com/@d3/learn-d3)
-* [API Reference](https://github.com/d3/d3/blob/master/API.md)
+* [API Reference](https://github.com/d3/d3/blob/main/API.md)
 * [Releases](https://github.com/d3/d3/releases)
 * [Examples](https://observablehq.com/@d3/gallery)
 * [Wiki](https://github.com/d3/d3/wiki)
