Backport Option.orElse from effect/

[george-wilson-rea]

There is precedent for this naming in Scala

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[gcanti]

Thanks @george-wilson-rea, though I would backport orElse from Effect as a "dual", auto-widening function, see (https://github.com/Effect-TS/data/blob/ba31af7b1a98f804e1a78fa82a2a8d558b119eb6/src/Option.ts#L415)

/cc @sukovanej

So, adapted to fp-ts, something like:

/**
 * Returns the provided `Option` `that` if `self` is `None`, otherwise returns `self`.
 *
 * @param self - The first `Option` to be checked.
 * @param that - The `Option` to return if `self` is `None`.
 *
 * @example
 * import * as O from "fp-ts/Option"
 *
 * assert.deepStrictEqual(O.orElse(O.none, () => O.none), O.none)
 * assert.deepStrictEqual(O.orElse(O.some(1), () => O.none), O.some(1))
 * assert.deepStrictEqual(O.orElse(O.none, () => O.some('b')), O.some('b'))
 * assert.deepStrictEqual(O.orElse(O.some(1), () => O.some('b')), O.some(1))
 *
 * @category error handling
 * @since 2.16.0
 */
export const orElse: {
  <B>(that: LazyArg<Option<B>>): <A>(self: Option<A>) => Option<A | B>
  <A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<A | B>
} = dual(2, <A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<A | B> => (isNone(self) ? that() : self))

p.s.
"dual" means that you can use the function both data-first and data-last:

pipe(self, orElse(that)) // data-last
orElse(self, that) // data-first

[george-wilson-rea]

Thanks, I've updated the PR to exactly what you posted there. Hopefully it's good now.