Add automatic check of angular selector to avoid breaking stackblitz demo

[divdavem]

For each Angular sample, we should never add a selector in the main component to avoid breaking the sample in stackblitz (which includes the main component with <ng-component>).

Is your feature request related to a problem? Please describe. This is to avoid opening PRs such as this one

Describe the solution you'd like We could add an eslint rule. If we want to avoid any kind of issues with stackblitz, we could also automatically test all samples in stackblitz with Playwright (but running those tests would require a lot of time).