[preset-env] v8 scope - batch 2

[romainmenke]

• importFrom and exportTo removal
• custom-selectors needs to use :is() like nesting
• custom-media has many outstanding issues of which some might require a breaking change

Best done against main and ported to 8 :

• case insensitive keyword, property and selector matching in plugins
• ensure nodes are revisited after any change by consistently using clones and never just assigning new values to node properties

[romainmenke]

To be released :

• css-tokenizer
• css-parser-algorithms
• media-query-list-parser
• postcss-custom-selectors
• postcss-custom-properties
• postcss-custom-media
• postcss-cascade-layers
• postcss-preset-env

[Antonio-Laguna]

@romainmenke this is now completed and should be good to be closed :)

[romainmenke]

Sweet 🎉