Consider removing fallback value for `site_url`?

[jfly]

I just spent a while trying to figure out why a gatsby generated rss feed included links to this repo. After much searching, I discovered this fallback code: https://github.com/dylang/node-rss/blob/1.2.2/lib/index.js#L36. This doesn't feel like a very sane default to me. (I don't think there is a sane default one could have here.)

The docs in readme.md (https://github.com/dylang/node-rss/tree/1.2.2#feedoptions) do not declare this as optional:

 * `site_url` **url string** Url to the site that the feed is for.
 * `image_url` _optional_  **url string** Small image for feed readers to use.

Could we instead throw an exception if site_url is not specified?

[adriancuadrado]

If an exception was thrown it would break backwards compatibility because it would stop for those who didn't specify any value.

Maybe for the next major release?

[jfly]

I'd argue this is justified as it would be fixing a bug (or helping people fix a bug in their code).

However, fixing this in a subsequent major release sounds better than not doing it!