Update README.

README.md

@@ -43,3 +43,15 @@ Or import everything into a namespace (here, `d3`):
 ```js
 import * as d3 from "d3";
 ```
+
+In Node:
+
+```js
+var d3 = require("d3");
+```
+
+You can also require individual modules and combine them into a `d3` object using [Object.assign](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign):
+
+```js
+var d3 = Object.assign({}, require("d3-format"), require("d3-geo"), require("d3-geo-projection"));
+```