fix(types): export ComponentOptionsMixin (#1361)

The newly introduced `ComponentOptionsMixin` was not re-exported.

packages/runtime-core/src/index.ts

@@ -159,6 +159,7 @@ export {
 } from './component'
 export {
   ComponentOptions,
+  ComponentOptionsMixin,
   ComponentOptionsWithoutProps,
   ComponentOptionsWithObjectProps,
   ComponentOptionsWithArrayProps,