Does not inject for content type text/xml, please fix line 389?

[nolandg]

When you crawl documents of type text/xml, the "response body is not HTML, skip injecting" warning is triggered and no cheerio/jsdom is injected.

I propose changing crawler.js:389 to:
if (!options.html && !typeis(contentType(response), ['html','xhtml','text/xml'])){
(include the 'text/xml')

When this is done, cheerio is injected and the XML document is parsed correctly and res.$ works great.

Thanks for the great package!

[mike442144]

hey, it seems good, could you open a pull request?