Add chainFirstEitherK(W) in ReaderTaskEither module

package.json

@@ -1,6 +1,6 @@
 {
   "name": "fp-ts",
-  "version": "2.11.5",
+  "version": "2.11.4",
   "description": "Functional programming in TypeScript",
   "main": "lib/index.js",
   "module": "es6/index.js",

src/ReaderTaskEither.ts

@@ -1156,6 +1156,24 @@ export const chainEitherKW: <E2, A, B>(
   f: (a: A) => Either<E2, B>
 ) => <R, E1>(ma: ReaderTaskEither<R, E1, A>) => ReaderTaskEither<R, E1 | E2, B> = chainEitherK as any
 
+/**
+ * Less strict version of [`chainFirstEitherK`](#chainfirsteitherk).
+ *
+ * @category combinators
+ * @since 2.12.0
+ */
+export const chainFirstEitherKW: <E2, A, B>(
+  f: (a: A) => Either<E2, B>
+) => <R, E1>(ma: ReaderTaskEither<R, E1, A>) => ReaderTaskEither<R, E1 | E2, A> = (f) => chainFirstW(fromEitherK(f))
+
+/**
+ * @category combinators
+ * @since 2.12.0
+ */
+export const chainFirstEitherK: <E, A, B>(
+  f: (a: A) => Either<E, B>
+) => <R>(ma: ReaderTaskEither<R, E, A>) => ReaderTaskEither<R, E, A> = chainFirstEitherKW
+
 /**
  * @category constructors
  * @since 2.0.0

test/ReaderTaskEither.ts

@@ -420,6 +420,11 @@ describe('ReaderTaskEither', () => {
     U.deepStrictEqual(await pipe(_.right('a'), _.chainEitherK(f))(undefined)(), E.right(1))
   })
 
+  it('chainFirstEitherKW', async () => {
+    const f = (s: string) => E.right<string, number>(s.length)
+    U.deepStrictEqual(await pipe(_.right<{}, number, string>('a'), _.chainFirstEitherKW(f))({})(), E.right('a'))
+  })
+
   it('chainIOEitherK', async () => {
     const f = (s: string) => IE.right(s.length)
     U.deepStrictEqual(await pipe(_.right('a'), _.chainIOEitherK(f))(undefined)(), E.right(1))