New Sniff: `Privacy.NoURLShorteners`

[dingo-d]

Issue Title

A new sniff should be aded in a new category called Privacy. It reflects the rule in the handbook

No URL shorteners used in the theme.

Issue Content

Rule type:

Error: No URL shorteners used in the theme.

Rule:

Handbook rule

URL shorteners are a possible security risk since they obfurscate the link destination, and can point to a malicious web sites containing spam or maleware. They are explicitly forbidden in the themes on wordpress.org.

List of URL shorteners:

https://goo.gl/ https://bitly.com/ https://polrproject.org/ https://www.rebrandly.com/ https://tinyurl.com/ https://hootsuite.com/pages/owly https://is.gd/ https://buffer.com/ http://adf.ly/ https://bit.do/

I'm planning on writing a sniff for this, I'll generate few shortened links that I'll provide in the unit tests. These should be checked against in enqueue functions, HTML anchor and link elements, readme files and JS files as well.

To do:

• [x] Create unit tests
• [x] Create new sniff

[jrfnl]

FYI: readme files can not easily be checked with PHPCS (unless we use a dirty hack which will not benefit the results).

And what about CSS files ? These may contain url(http://externalsite.com/something) values too.

[dingo-d]

For now we can focus on checking css, php and js files (non minified). And then I could add in the theme sniffer a way to just go through the readme and check there for shortened link using a regex (an idea).

[jrfnl]

Closing as fixed by PR #216.