Add general page component

[juri-sinitson]

TODOs

Add the general page component CommonPage which will be used in every frontend app of my open source angular monorepo (https://github.com/juri-sinitson/angular-monorepo) to the libary shared-ui-common (https://github.com/juri-sinitson/angular-monorepo/tree/main/libs/shared/ui-common) by the following steps:

1. Download and apply this free theme: https://sakai.primeng.org/ and switch this theme in https://github.com/juri-sinitson/angular-monorepo/blob/main/styles.scss

2. Create the component CommonPage with the router outlet on it. This component should receive the menu structure by the classical @input. Figure out how this structure looks like in this theme and adjust the types accordingly.

3. Adjust the existent storybook stories to show their stories on CommonPage. For stories a route with a single home entry should be used.

4. The router config should be provided for the topmost component. In the stories mock the Router subproviders when necessary.

5. Also create a story for the CommonPage. Generate 2 fictive entires with 3 fictive subentries each. With the interactive tests:
   a. Make sure, those menu entries are really visible.
   b. Make sure the theme switcheer works as expected.

6. Adjust the frontend apps and their e2e tests accordingly.

NOTE!

Before implementing this it seems to be reasonable to wait until styled and unstyled modes become available in PrimeNG.
See also:
https://primeng.org/roadmap
https://www.youtube.com/watch?v=MYkoX6WmhiE