feat: add extends types

Author: pengzhanbo

src/config/extends.d.ts

@@ -0,0 +1,18 @@
+import type { LiteralUnion } from '../utils'
+
+export interface CustomExtends {}
+
+export type KnownExtends = LiteralUnion<
+  | 'stylelint-config-standard'
+  | 'stylelint-config-standard-scss'
+  | 'stylelint-config-recess-order'
+  | 'stylelint-config-rational-order'
+  | 'stylelint-config-prettier'
+  | 'stylelint-config-prettier-scss'
+  | 'stylelint-config-recommended-vue'
+  | 'stylelint-config-sass-guidelines'
+  | 'stylelint-config-primer'
+  | 'stylelint-config-wikimedia'
+  | 'stylelint-config-wordpress'
+  | keyof CustomExtends
+>