fix(Mixin): export MixinFactory type for ease of use

src/declarations/stencil-public-runtime.ts

@@ -6,10 +6,6 @@ declare type CustomMethodDecorator<T> = (
 
 type UnionToIntersection<U> = (U extends any ? (x: U) => void : never) extends (x: infer I) => void ? I : never;
 
-type MixinFactory = <TBase extends abstract new (...args: any[]) => any>(
-  base: TBase,
-) => abstract new (...args: ConstructorParameters<TBase>) => any;
-
 export interface ComponentDecorator {
   (opts?: ComponentOptions): ClassDecorator;
 }
@@ -407,15 +403,21 @@ export declare function readTask(task: RafCallback): void;
  */
 export declare const setErrorHandler: (handler: ErrorHandler) => void;
 
+export type MixinFactory = <TBase extends new (...args: any[]) => any>(
+  base: TBase,
+) => abstract new (...args: ConstructorParameters<TBase>) => any;
+
 /**
  * Compose multiple mixin classes into a single constructor.
  * The resulting class has the combined instance types of all mixed-in classes.
  *
  * Example:
  * ```
- * const AWrap = (Base) => {class A extends Base { propA = A }; return A;}
- * const BWrap = (Base) => {class B extends Base { propB = B }; return B;}
- * const CWrap = (Base) => {class C extends Base { propC = C }; return C;}
+ * import { Mixin, MixinFactory } from '@stencil/core';
+ *
+ * const AWrap: MixinFactory = (Base) => {class A extends Base { propA = A }; return A;}
+ * const BWrap: MixinFactory = (Base) => {class B extends Base { propB = B }; return B;}
+ * const CWrap: MixinFactory = (Base) => {class C extends Base { propC = C }; return C;}
  *
  * class X extends Mixin(AWrap, BWrap, CWrap) {
  *   render() { return <div>{this.propA} {this.propB} {this.propC}</div>; }

src/internal/stencil-core/index.d.ts

@@ -40,6 +40,7 @@ export {
   Listen,
   Method,
   Mixin,
+  MixinFactory,
   Prop,
   readTask,
   render,