Create a linter rule that will disallow adding cross-package imports in the ckeditor5-watchdog package

[ma2ciek]

A follow-up to #9315.

We need to disallow cross-package imports in the ckeditor5-watchdog package as this might lead to duplication errors in our integrations (see #9315).

The information should be also added to our docs.

[Reinmar]

In #9315 we decided to simply remove that dependency for now.

[pomek]

Scope:

• Create a new rule that disallows importing things from ckeditor5 and ckeditor5-* (https://github.com/ckeditor/eslint-plugin-ckeditor5-rules/)
• Configure ckeditor5-watchdog to use this rule. (https://github.com/ckeditor/eslint-config-ckeditor5)

Helpful resources:

• https://eslint.org/docs/developer-guide/working-with-rules