feat(store): enable immutability checks by default

[evgenyfedorenko]

Closes #2217

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?
Store runtime immutability checks are being enabled by default with this change

[ ] 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?

Currently immutability checks are opt in.

Closes #2217

What is the new behavior?

If state or action is mutated then there will be a run time exception thrown by default now. In order to opt out user will need to pass immutability checks set to false.

Does this PR introduce a breaking change?

[x] Yes
[] No

BREAKING CHANGE

Before
Immutability checks are opt-in.

After
Immutability checks are enabled by default. If state or action is mutated then there will be a run time exception thrown.

[evgenyfedorenko]

Please let me know if there is anything else I need to add/correct.

[ngrxbot]

Preview docs changes for b78c59a at https://previews.ngrx.io/pr2266-b78c59a/

[timdeschryver]

LGTM 👍
We should also remove the runtime checks from the schematics (https://github.com/ngrx/platform/blob/master/modules/schematics/src/store/index.ts#L75) in a separate PR.

[timdeschryver]

@evgenyfedorenko could you also add a breaking change note to the PR please, you can find a template in CONTRIBUTING.MD

[evgenyfedorenko]

@evgenyfedorenko could you also add a breaking change note to the PR please, you can find a template in CONTRIBUTING.MD

Done