📚 - Find a way to reuse logic with all host-declarations between public and proprietary `demo`-apps

[nsbarsukov]

Description

We often have bugs in our proprietary demo that we forget to sync public app.template.html with proprietary app.template.html.

https://github.com/Tinkoff/taiga-ui/blob/8c72e478e3d6907a98e48b52551d77b46d50e88c/projects/demo/src/modules/app/app.template.html#L40-L44

Find a solution to reuse this the same logic between public and proprietary demo.