I usually put minified JS files in a two-level subfolder (
<vendor>/<addon>) of 
js and use the unminified version within 
_files for development.
So I'd probably have the file in 
src/addons/Andrew/Articles/_files/js/andrew/articles/reading-progress.js
In the template this would be referenced as
	
	
	
		Code:
	
	
		<xf:js addon="Andrew/Articles" src="andrew/articles/reading-progress.js"  min="1" />
	 
 (No need to change this, works for production and dev).
To build the Add-on a 
build.json is required
	
	
	
		Code:
	
	
		{
  "additional_files": [
    "js/andrew/articles/reading-progress.js"
  ],
  "minify": [
    "js/andrew/articles/reading-progress.js"
  ]
}
	 
 
In order to use the unminified JS file from 
_files (via 
devjs.php) the following code in 
config.php ist required as well (as already mentioned):
	
	
	
		PHP:
	
	
		$config['development']['fullJs'] = true;