Document justification for dangerouslySetInnerHTML={{__html: ...}}

[syranide]

From #1515 (comment)

[jimfb]

cc @zpao

[syranide]

@JSFB FYI, what I was referring to was the idea that {__html: } should preferably be considered a "type/taint" of sorts, to be used as function createMarkup() { return {__html: ''}; }; <div dangerouslySetInnerHTML={createMarkup()} /> and not for it to be created immediately inside dangerouslySetInnerHTML={{__html: ''}}.

The point being that if you unintentionally do say <div dangerouslySetInnerHTML={getUsername()} /> it will not be rendered because getUsername() would return a plain string and not a {__html: ''} object.

[jimfb]

@syranide Great, thanks. Fixed in the latest version. Better?