Spinner code example lacks module import in documentation

[meherhendi]

Issue type

I'm submitting a ...

• [X] bug report
• [ ] feature request

Issue description

the spinner documentation code examples lack the module import of NbSpinnerModule in app.module.ts

Current behavior: The code examples shows the component's typescript file only Expected behavior: Have a second tab that displays the import of NbSpinnerModule in app.module.ts

Steps to reproduce: open spinner module documentation and see examples

[sasidharansd]

Hey @meherhendi, Think they already have in the docs on how to import it into the modules.