Update iff predicates typings to be either sync or async

[NickBolles]

Summary

• Tell us about the problem your pull request is solving.
  The iff* hooks were typed to only accept synchronous predicate functions
  This PR adds

1. Typescript type definitions for Asynchronous (in addition to the previous synchronous), Predicate functions
2. Typescript type tests (in types/tests.ts) to test for Async Predicates
3. 2 more tests for Iffelse to get it to 100% code coverage in normal (non-typescript) tests

• Are there any open issues that are related to this?
  No
• Is this PR dependent on PRs in other repos?
  no

If so, please mention them to keep the conversations linked together.

Other Information

There are a few small updates to docs to happen, there are more after my next PR

iffElse

arguments - {Function} predicate -> {Boolean | Promise | Function} predicate

iffElse

arguments - {Function | Boolean} predicate -> {Boolean | Promise | Function} predicate

[eddyystop]

The predicate can already be a function which returns a Promise. Hence the function can be asynchronous, even an async function. I'm not not clear on what feature this PR adds.

[NickBolles]

@eddyystop I think you miss-read the title. This is for the typescript types. They were previously restricted to synchronous predicate functions, which is incorrect.

I added the typescript types for both Sync or Async Predicate functions, as well as Typescript type tests for IFF, and a normal test to make test coverage 100%. (I'll update the OP with this info)