docs(eslint-plugin): add docs for signal-state-no-arrays-at-root-level

[iErKy]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https:/ngrx/platform/blob/main/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)
[ ] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Closes #4501

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x ] No

Other information

[netlify]

✅ Deploy Preview for ngrx-io ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	29f9475
🔍 Latest deploy log	https://app.netlify.com/sites/ngrx-io/deploys/66fef72fc7601b0008ddf4a4
😎 Deploy Preview	https://deploy-preview-4549--ngrx-io.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[timdeschryver]

Thanks for the PR @iErKy .
You can ignore the failing build, this is something not related to this PR.

[timdeschryver]

Suggested change

	This rule ensure that a Signal State shouldn't accept an array type at root level.
	This rule ensure that a Signal State shouldn't accept an array type at the root level.

[timdeschryver]

Formatting:

Suggested change

	```ts
	```ts

[timdeschryver]

Formatting:

Suggested change

	```ts
	const store = withState([1, 2, 3]);
	```
	```ts
	const store = withState([{ foo: 'bar' }]);
	```
	```ts
	const store = withState<string[]>([]);
	```
	```ts
	const initialState = [];
	const store = withState(initialState);
	```
	```ts
	const store = withState([1, 2, 3]);

const store = withState([{ foo: 'bar' }]);

const store = withState<string[]>([]);

const initialState = [];
const store = withState(initialState);

[iErKy]

@timdeschryver will fix comments and push changes.

[timdeschryver]

Thanks @iErKy