Add instructions on how to unminify main.js for easier browser debugg…

…ing (mmistakes#3055)

* Add instructions on how to unminify main.js for easier browser debugging

* Fixed Markdown style like sggested by @iBug

docs/_docs/17-javascript.md

@@ -64,3 +64,18 @@ To get started:
 {: .notice--warning}
 
 If all goes well, running `npm run build:js` will compress/concatenate `_main.js` and all plugin scripts into `main.min.js`.
+
+## Debugging
+The minified Javascript is harder to debug in the browser than the raw source. To stop the minification and just bundle all the Javascript as-is; open up `package.json` and edit the value `scripts.uglify` from:
+
+```json
+  "scripts": {
+    "uglify": "uglifyjs [...] -c -m -o assets/js/main.min.js",
+```
+
+to simply concatenating the files:
+
+```json
+  "scripts": {
+    "uglify": "cat [...] > assets/js/main.min.js",
+```