Features/custom namespaces and elements

[joe1chen]

Add ability to customize namespaces and elements. This supercedes pull #69.

Examples:

Custom namespace:

feed.namespaces = {
  "xmlns:dcterms": "https://purl.org/dc/terms/",
  "xmlns:media": "https://search.yahoo.com/mrss/"
};

Custom elements at root:

feed.elements = [{
  'custom1': [{
    _attr: {
      attr1: 'value1'
    }
  }, {
    'custom2': 'value2'
  }]
}];

Custom elements in item:

posts.forEach(post => {
  feed.addItem({
    title: post.title,
    id: post.url,
    elements: [{
      'media:content': [{
        _attr: {
          url: 'https://v3spec.msn.com/image1.jpg',
          type: 'image/jpeg',
          medium: 'image'
        }
      }, {
        'media:credit': 'Joe Gargery/Fabrikam Images'
      }]
    }]
  });
});

[coveralls]

Coverage decreased (-1.3%) to 94.313% when pulling 63ee652 on joe1chen:features/custom_namespaces_and_elements into eb08b96 on jpmonette:master.

[itsMattShull]

Is there anything I can do to help reconcile the conflicts and get this pull request merged?

[jpmonette]

@derekshull Thanks for your time. Main things that needs to be addressed are the following:

• Rename the elements attributes to extra
• Make sure the data structure provided via extra is xml-js-friendly
• Get rid of the feedLinks as it seems to be out-of-scope
• Make sure to support RSS, Atom and JS feed (where applies)
• Resolve conflicts

Feel free to spin up a new PR & I'll review 🚀.

[mikestopcontinues]

How does this relate to extensions? If I understand correctly, they're two ways of describing the same thing. Shouldn't they be merged?