feat: add ng add support for standalone config to NgRx packages

[brandonroberts]

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?

[x] 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 #

What is the new behavior?

Fixed bug with syncing schematics-core across packages.

Adds ng add support for NgRx packages

ng add @ngrx/effects --standalone
ng add @ngrx/store-devtools --standalone
ng add @ngrx/router-store --standalone

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

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[markostanimirovic]

🚀

[DMezhenskyi]

Looks great! 👍
I have just one question. Shouldn't be the install.md files for corresponding modules also updated on ngrx.io documentation? I am curious because the checkbox "Documentation has been added/updated" is checked but I could not see md files updated.

[brandonroberts]

@DMezhenskyi yep, good catch. I just updated those also