Add ignore config to no-unknown-property rule

[insin]

Context: insin/babel-plugin-react-html-attrs#4

[ljharb]

As far as I know, React itself doesn't support "class" or "for", and requires "className" and "htmlFor". Can you point to some documentation that allows for this usage?

[insin]

React doesn't support it, but you can use Babel plugins to handle usage of 'class' and 'for' at transpile time for teams who prefer to keep using them, e.g: insin/babel-plugin-react-html-attrs#4 (comment)

[yannickcr]

That's a very specific use case, but I am not against adding such option.

Just a couple of things:

• I'd prefer to use an ignore option instead of allow (like prop-types or jsx-pascal-case)
• You are referring to your specific use case in the documentation. I think it can be confusing. Maybe just saying that you can ignore some properties is enough ?

[insin]

Changed the option to ignore and made the documentation more generic, as per other rules.

[yannickcr]

Merged, thanks!