HTTP/2 and errorThrown or statusText

[vkrol]

Hello!

In HTTP/2 errorThrown and statusText will be the empty strings:

HTTP/2 does not define a way to carry the version or reason phrase that is included in an HTTP/1.1 status line.
https://tools.ietf.org/html/rfc7540#section-8.1.2.4

I think that it should be added to this page https://api.jquery.com/jQuery.ajax/.

[mgol]

Would you like to submit a PR?