fix(router-store): include string[] as return type for selectQueryParam

[timdeschryver]

PR Checklist

Please check if your PR fulfills the following requirements:

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

PR Type

What kind of change does this PR introduce?

[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:

What is the current behavior?

Closes #4286

What is the new behavior?

Does this PR introduce a breaking change?

[x] Yes
[ ] No

BREAKING CHANGE:

BEFORE:
The return type of `selectQueryParam` is `MemoizedSelector<V, string | undefined>`.

AFTER:
The return type of `selectQueryParam` now includes `string[]`, making the return type `MemoizedSelector<V, string | string[] | undefined>`.

Other information

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