compatMode when reporting an issue

[karlcow]

I wonder if it could speed up some type of bugs to add automatically add the mode of the document.

When reporting an issue, the information about document.compatMode could be sent to the form and a label created when the document is in Quirks Mode , maybetype-quirksmode. And probably to not add a label when it's in standard mode.

[miketaylr]

Do we know how many issues are caused by quirksmode? (but yeah, this is probably trivial to add)

[karlcow]

Probably difficult to identify.
except if we already did a diagnosis concluding that it could be quirk mode.

https://github.com/webcompat/web-bugs/issues?q=is%3Aissue++%22quirk+mode%22+in%3Abody