message: WIP: add let to demo
diff: import { pipe } from "../../Function"
  import * as T from "../Effect"
  -pipe(
  +const program = pipe(
  T.of,
  T.bind("foo", () => T.succeedNow(1)),
  T.merge(() => T.sequenceS({ bar: T.succeedNow(2), baz: T.succeedNow(3) })),
  + T.let("red", () => 4),
  T.tap((s) =>
  T.effectTotal(() => {
  console.log(s)
  })
  - ),
  - T.runMain
  )
  +)
  +
  +T.runMain(program)
  