[docs] Add documentation for new file browser public APIs

[Harshg999]

What changes were proposed in this pull request?

• Added docs section for all new filebrowser APIs

How was this patch tested?

• Manually

[Harshg999]

Thank you @pychheda and @bjornalm for your detailed review! I've incorporated the suggestions and rephrased most of the lines.

Can you please review again to see if I'm are missing anything? Thanks!