fix(effects): export CreateEffectMetadata

[alex-okrushko]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

Re-exports CreateEffectMetadata that was added to the createEffect(...) signature recently.

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

Closes # #2243

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[ngrxbot]

Preview docs changes for 307cb5f at https://previews.ngrx.io/pr2245-307cb5f/

[timdeschryver]

👍

I didn't know it should be exported to be able to build a lib... it isn't giving any problems while building the application itself.