chore: update directives description

Author: sxzz

README.md

@@ -287,7 +287,7 @@ Components({
 
   // auto import for directives
   // default: `true` for Vue 3, `false` for Vue 2
-  // For Vue 2, there may be performance losses during compilation and runtime.
+  // Babel is needed to do the transformation for Vue 2, it's disabled by default for performance concerns.
   directives: true,
 
   // filters for transforming targets

src/types.ts

@@ -129,7 +129,7 @@ export interface Options {
    *
    * default: `true` for Vue 3, `false` for Vue 2
    *
-   * For Vue 2, there may be performance losses during compilation and runtime.
+   * Babel is needed to do the transformation for Vue 2, it's disabled by default for performance concerns.
    * @default undefined
    */
   directives?: boolean