Add note about individual methods

Author: eliot-akira

README.md

@@ -22,6 +22,12 @@ const logo = path.join('./assets/img', filename);
 document.querySelector('#logo').src = logo;
 ```
 
+Methods under `path` can be imported individually.
+
+```javascript
+import { join } from '@isomorphic-git/path';
+```
+
 If your project uses CommonJS, this is also supported.
 
 ```javascript