build: add Nx workspace support

[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?

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

What is the current behavior?

• Adds support for using an Nx workspace to build/test the NgRx libraries.
• We will still have Bazel for build and deployment of npm packages, as this is considered a potential breaking change, but we will use Nx for all other tasks.
• The Bazel BUILD files will remain.
• Further tooling will be added for better release support

Closes #

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[ngrxbot]

Preview docs changes for 45c2117 at https://previews.ngrx.io/pr2535-45c2117/

[timdeschryver]

From what I can see this looks good!
I just have some problems building the project locally due to that I'm working on a Windows machine.

@brandonroberts I think that when the conflicts are resolved we could merge this in?

In a follow-up PR we could clean up the warnings while running the tests, and it also seems like ts-jest isn't too happy about the component tests (this could be from before).

[timdeschryver]

Forgot about the example app... 😅
It seems like the tests don't run locally (could be me) while running yarn example:test

An unhandled exception occurred: Project 'example-app' does not support the 'test' target.
See "C:\Users\TDESCH~1\AppData\Local\Temp\ng-hYm7L5\angular-errors.log" for further details.

And I also think that the example tests aren't run during the CI.

[brandonroberts]

I'll get the copy commands cleaned up, and the example app test target. The Bazel build also broke while upgrading the packages 😞 so I'll need to either fix that, or we just leave it and switch over officially for V10.