feat(router-store): new selector factory selectRouteDataParam (#3673)

[samuelfernandez]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https:/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?

[ ] Bugfix
[x] 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:

What is the current behavior?

Closes #3673

What is the new behavior?

New selector factory for route data param

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

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[timdeschryver]

LGTM.
We should also update the docs https://ngrx.io/guide/router-store/selectors

[samuelfernandez]

LGTM.

We should also update the docs https://ngrx.io/guide/router-store/selectors

@timdeschryver I checked that, and the only thing that changes as far as I've seen is the example already included in this PR. Those docs reference the example, but don't have explicit references

[timdeschryver]

@samuelfernandez yep, you're right. My bad!