Add autofix to font-weight-notation

[hiroppy]

I read https://github.com/stylelint/stylelint/blob/master/docs/developer-guide/rules.md#adding-an-option-to-an-existing-rule and write this issue.

I already have written code.
see hiroppy@2977230

Details

numeric

a { font-weight: normal; } -> a { font-weight: 400; }
a { font: italic bold 20px; } -> a { font: italic 700 20px; }

named-where-possible

a { font-weight: 400; } -> a { font-weight: normal; }
a { font: italic 700 20px; } -> a { font: italic bold 20px; }

If this request is accepted, I will submit PR :)

[alexander-akait]

@abouthiroppy PR welcome!

[jeddy3]

Fixing #3855 (comment) is a prerequisite to adding autofix.

See also: #3159 (comment)

[FloEdelmann]

@hiroppy Sorry for the ping in this old issue, but given you've already written the code for the autofix, would you fancy opening a PR?

I think @jeddy3's comment is already resolved (#3855 was closed by #6005). I don't know if that requires changes in your code though.

[ybiquitous]

@FloEdelmann Thanks for the reminder. I'm going to work on this. 💪🏼