Supporting custom namespaces?

No source file or test is named in the issue. Start by locating the RSS/Atom parser entry point and its handling of element names, then use the sample feed to check whether the custom books:bookid field is preserved alongside standard fields.

Hey there, love what you're doing here Dave to make things simple and easy to use :)

Question - should this parse custom namespaces? For example, I'm playing around with adding structured data for a "books" rss project and made a mockup here:

https://wooden-honorable-kale.glitch.me/feed.xml

So this code:

<item>
<title>Testing new fields</title>
<description>Some description </description>
<pubDate>Thu, 16 Jun 2022 00:00:00 +0000</pubDate>
<books:bookid>https://openlibrary.org/works/OL19098683W</books:bookid>
<link>http://tomcritchlow.com/2022/06/16/rejecting-specialization/</link>
<guid isPermaLink="true">http://tomcritchlow.com/2022/06/16/rejecting-specialization/</guid>
</item>

Get's parsed using reallysimple as:

        {
            "title": "Testing new fields",
            "description": "Some description",
            "pubDate": "2022-06-16T00:00:00.000Z",
            "link": "http://tomcritchlow.com/2022/06/16/rejecting-specialization/",
            "guid": "http://tomcritchlow.com/2022/06/16/rejecting-specialization/"
        }

Ideally I'd like to generate something like this:

        {
            "title": "Testing new fields",
            "description": "Some description",
            "pubDate": "2022-06-16T00:00:00.000Z",
           "books:bookid":"https://openlibrary.org/works/OL19098683W"
            "link": "http://tomcritchlow.com/2022/06/16/rejecting-specialization/",
            "guid": "http://tomcritchlow.com/2022/06/16/rejecting-specialization/"
        }

I'm a bit of a coding beginner (and not sure if I coded the custom namespace correctly?) so forgive me if this doesn't make sense or I'm doing something wrong