Remove undefined from keyof result of (Pick|Omit)ByValue(Exact)?

[vatosarmat]

Related issues:

• Resolved keyof PickByValue<ObjectWithOptionals, SomeType> gives union with undefined #123

Checklist

• I have read CONTRIBUTING.md
• I have linked all related issues above
• I have rebased my branch

For bugfixes:

• I have added at least one unit test to confirm the bug have been fixed
• I have checked and updated TOC and API Docs when necessary

For new features:

• I have added entry in TOC and API Docs
• I have added a short example in API Docs to demonstrate new usage
• I have added type unit tests with dts-jest

[piotrwitek]

Hey @vatosarmat ,
Thanks for the PR, could you please refresh your fork and rebase your branch because there are some unrelated changes in your commits and it's very difficult to review the changes.

Thanks.

[vatosarmat]

@piotrwitek done

[piotrwitek]

Looks good, great job and thanks for contribution @vatosarmat!