docs: enhance NcAppSidebar documentation

- join some simple examples into one
- wrap all examples in mock of NcAppContent > NcContent with basic styling (these components can not be used in examples several times on one page)
- implement open/close logic for all examples
- fix some typos in comments and docs
- lint file

Signed-off-by: Maksim Sukharev <[email protected]>

Author: Antreesy