breaking change of postcss-selector-parser v7

In version 6.1.2, the following code outputs 1, but in version 7.0.0, it outputs 2. The reason is that selector.each executes once more after insertAfter. This caused an issue for Vue when upgrading to postcss-selector-parser v7

step to reproduce

• 1.clone this repo
• 2.run npm install
• 3.run npm run dev
• 4.change the version of postcss-selector-parser in package.json to 6.1.2
• 5.repeat step 2 and 3