fix(component-store): export EffectReturnFn interface

[alex-okrushko]

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• 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)
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PR Type

What kind of change does this PR introduce?

Export EffectReturnFn as well, otherwise we get an error:

error TS4029: Public property 'effectName' of exported class has or is using name 'EffectReturnFn' from external module "path/to/ngrx/modules/component-store/src/component-store" but cannot be named

[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:

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[ngrxbot]

Preview docs changes for b9b4253 at https://previews.ngrx.io/pr2555-b9b4253/