Add missing Either.void constructor (#4413)

Author: gcanti

.changeset/thick-laws-yell.md

@@ -0,0 +1,5 @@
+---
+"effect": minor
+---
+
+Add missing `Either.void` constructor.

packages/effect/src/Either.ts

@@ -118,6 +118,15 @@ export declare namespace Either {
  */
 export const right: <R>(right: R) => Either<R> = either.right
 
+const void_: Either<void> = right(void 0)
+export {
+  /**
+   * @category constructors
+   * @since 3.13.0
+   */
+  void_ as void
+}
+
 /**
  * Constructs a new `Either` holding a `Left` value. This usually represents a failure, due to the right-bias of this
  * structure.

packages/effect/test/Either.test.ts

@@ -13,6 +13,10 @@ import {
 } from "effect/test/util"
 
 describe("Either", () => {
+  it("void", () => {
+    deepStrictEqual(Either.void, Either.right(undefined))
+  })
+
   it("gen", () => {
     const a = Either.gen(function*() {
       const x = yield* Either.right(1)