docs(developer): add description of npm-run to run locally installed npm scripts (angular#13765)

PR Close angular#13765

Author: BendingBender

DEVELOPER.md

@@ -71,7 +71,13 @@ particular `gulp` and `protractor` commands. If you prefer, you can drop this pa
 Since global installs can become stale, and required versions can vary by project, we avoid their
 use in these instructions.
 
-*Option 2*: defining a bash alias like `alias nbin='PATH=$(npm bin):$PATH'` as detailed in this
+*Option 2*: globally installing the package `npm-run` by running `npm install -g npm-run`
+(you might need to prefix this command with `sudo`). You will then be able to run locally installed
+package scripts by invoking: e.g., `npm-run gulp build`
+(see [npm-run project page](https://github.com/timoxley/npm-run) for more details).
+
+
+*Option 3*: defining a bash alias like `alias nbin='PATH=$(npm bin):$PATH'` as detailed in this
 [Stackoverflow answer](http://stackoverflow.com/questions/9679932/how-to-use-package-installed-locally-in-node-modules/15157360#15157360) and used like this: e.g., `nbin gulp build`.
 
 ## Installing Bower Modules