message: fix: set negative number is does not work
diff: import { Theme } from '@styli/theming'
  import { Plugin } from './types'
  -const isPlainDirective = (key: string) => /^\w+(-\w+)?$/.test(key)
  +const isPlainDirective = (key: string) => /^\w+(--?\w+)?$/.test(key)
  export const coreMiddleware: Plugin = {
  name: 'styli-plugin-core',
  