Add support for Twitter cards metadata in html-metadata
See the full task at https://phabricator.wikimedia.org/T148835
Twitter cards are a type of metadata in a webpage that gives information about how to cite the resource. There is a good explanation about them here: https://dev.twitter.com/cards/overview
Here's an example of a page with Twitter metadata: view-view-source:http://www.aftenposten.no/kultur/Pinlig-for-Skaber-555558b.html
You should create a function called exports.twitter in https://github.com/wikimedia/html-metadata/blob/master/lib/index.js that scrapes all the twitter tags, and creates a javascript object. This object should contain all of the tag names as keys and contains the content of the tag as the value. If there are multiple values for the same tag name, these should be in an Array. You should also register the method in https://github.com/wikimedia/html-metadata/blob/master/index.js
You should also create tests for your new function. You can put tests of a live website in https://github.com/wikimedia/html-metadata/blob/master/test/scraping.js. You can also create tests of a static website in https://github.com/wikimedia/html-metadata/blob/master/test/static.js. You may find it helpful to write these tests early on in writing your function, as they will help you verify your function is working correctly. Tests can be run by doing
npm test