Consider to include abilities of stylelint-processor-styled-components

[chinesedfan]

Hi, I am one of maintainers of stylelint-processor-styled-components. Before stylelint supports syntax: css-in-js, users lint styles with the processor.

As discussed in stylelint-processor-styled-components#278, postcss-jsx analyzes the whole AST more completely and can give more accurate replacements for tagged template interpolations, so hope it can include as much as possible abilities of stylelint-processor-styled-components and make the processor deprecated.

Now main differences between them are, which are listed with test files names of stylelint-processor-styled-components,

1. not require keeping closing backtick on base indentation level: ignore-rule-comments, see styled-compoents' document
2. not throw errors for invalid css: hard, nofiles
3. not support ignore comments: ignore-rule-comments
4. not support interpolation-tagging: interpolation-tagging
5. not support options: options, real-world
6. will throw unexpected errors if the interpolation is a declaration: interpolations

Not all of them are appropriate to implement in postcss-jsx, but if we really decided to deprecate the processor with postcss-jsx, we should write F.A.Q or some documents for users to migrate smoothly.

[alexander-akait]

/cc @gucong3000 friendly ping