docs(docs-infra): add top level banner component
- create top level banner component
- write unit tests
- close banner and keep state in the local storage
- fix: support screens of tablets and phones
PR Close#57458
To increase the ease of development we are moving @angular/docs into the adev directory within this repo. While
we are doing this to improve our development experience in the short term, efforts are also in place
to maintain a division between this @angular/docs (shared) code and adev itself, so that it can be extracted
back out in the future when components is ready to leverage it as well.
PR Close#57132
