feat(component-store): initial setup

[alex-okrushko]

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?

Skeleton for Component Store

[ ] 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?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[ngrxbot]

Preview docs changes for da77ee9 at https://previews.ngrx.io/pr2519-da77ee9/

[brandonroberts]

Side note: We should create a schematic for this, as we've had to this enough times with each new library

[timdeschryver]

component-store should also be added on the intro page

[timdeschryver]

@alex-okrushko can you also add it to the intro page?

[alex-okrushko]

Thanks @timdeschryver
I missed the initial comment about it somehow 🤦‍♂️

[timdeschryver]

👍