Expand status codes

[PENGUINLIONG]

According to https://developer.mozilla.org/en-US/docs/Web/HTTP/Status

[tomaka]

Looks good, thanks!
Coud you please also add an entry to the CHANGELOG?

[PENGUINLIONG]

I read the registry of HTTP status code reservation on IANA after that. Maybe it's a better option to use the IANA settings. But how about those WebDAV codes (like 208 Multi-Status, which is 208 Already Reported in IANA registry) already exist in this repo? Should those be kept and populated along with those HTTP codes?

EDIT WebDAV is not a problem actually. WebDAV codes are also registered. But I still wonder why Multi-Status has two different value in MDN's record.