Refactor .npmignore.
Refactor .npmignore.

Group together folders and files.

Also, ignore more files and folders like:

* gulp/
* lighthouse-cli/test/
* gulpfile.js
* .editorconfig
* .eslintignore
* .eslintrc.js
* latest.artifacts.log

GoogleChrome/lighthouse,arturmiz/lighthouse,cedricbellet/lighthouse,umaar/lighthouse,mixed/lighthouse,mixed/lighthouse,ev1stensberg/lighthouse,arturmiz/lighthouse,GoogleChrome/lighthouse,deepanjanroy/lighthouse,wardpeet/lighthouse,wardpeet/lighthouse,deepanjanroy/lighthouse,deepanjanroy/lighthouse,ev1stensberg/lighthouse,GoogleChrome/lighthouse,deepanjanroy/lighthouse,umaar/lighthouse,arturmiz/lighthouse,deepanjanroy/lighthouse,mixed/lighthouse,cedricbellet/lighthouse,GoogleChrome/lighthouse,cedricbellet/lighthouse,arturmiz/lighthouse,cedricbellet/lighthouse,tkadlec/lighthouse,ev1stensberg/lighthouse,umaar/lighthouse,wardpeet/lighthouse,cedricbellet/lighthouse,umaar/lighthouse,tkadlec/lighthouse,wardpeet/lighthouse,GoogleChrome/lighthouse,tkadlec/lighthouse,tkadlec/lighthouse,mixed/lighthouse,wardpeet/lighthouse,arturmiz/lighthouse,ev1stensberg/lighthouse