Update instructions and code sample to use standalone components instead of, or in addition, to NgModules

[nanophilip]

Could you please update the instructions and code sample at https://github.com/RaphaelJenni/FirebaseUI-Angular?tab=readme-ov-file#how-to-use to use standalone components instead of, or in addition to, NgModules?

And I believe it would be helpful to add filenames at the beginning of each code block like it is done at https://angular.dev/reference/migrations/standalone#convert-declarations-to-standalone:

How to use:

1. Using NgModules

// ./app/app.module.ts
...

2. Using standalone components

// ./app/app.component.ts
...

// ./main.ts
...

[katwekibs]

Am also stuck between these lines, could not figure out how to work with standalone components.