Fixed broken link in the readme (#390)

* Fixed broken link in the readme

Link to "task automation with npm" pointed to 404, now pointing to an archive of James` post with the same content.

* Changed link to archive.org mirror

README.md

@@ -25,7 +25,7 @@ Like `npm run watch-js & npm run watch-less` but better.
 
 ## Why
 
-I like [task automation with npm](https://github.com/substack/blog/blob/master/npm_run.markdown)
+I like [task automation with npm](https://web.archive.org/web/20220531064025/https://github.com/substack/blog/blob/master/npm_run.markdown)
 but the usual way to run multiple commands concurrently is
 `npm run watch-js & npm run watch-css`. That's fine but it's hard to keep
 on track of different outputs. Also if one process fails, others still keep running