Simplify namespace structure

[cmeeren]

While testing in #12 (comment), I noticed that I had to open separate namespaces to get the result and asyncResult instances, and yet another one (the main FsToolkit.ErrorHandling) to get the helpers (Result.xxx etc.).

I suggest that we make result and asyncResult available in the main namespace (perhaps other CEs too?). While I may be biased to my own usage, I guess that people using this library are very likely to want these builders, so we shouldn't require them to have three opens in every relevant file.

(I haven't investigated the rest of the namespace/module structure of FsToolkit.ErrorHandling; there might be other places we could simplify, too.)

[demystifyfp]

I agree. Will incorporate it in the new release.

[demystifyfp]

Fixed in 1.0.0