Add back deleted examples

[karlhorky]

Hi, thanks for this extra proposal repo! I was not up to date that this was split into a separate proposal.

I added an example back in 2021 to show that these proposals can be (in simple cases) used as a replacement for the npm package p-map by @sindresorhus (33M weekly downloads) and similar

• Examples originally added in https://github.com/tc39/proposal-iterator-helpers/pull/124 and https://github.com/tc39/proposal-iterator-helpers/pull/136
• Examples removed as part of https://github.com/tc39/proposal-iterator-helpers/pull/263