[docs] Add documentation improvements & OAuth examples

[joshuadeguzman]

Details

Hey @jorgefspereira, I'd like to propose to improve the documentation in order for other developers have a smooth integration with Plaid.

A few things I'd like to highlight:

1. Setting up apple-app-site-association guide, I can whip out a small draft or link to a helpful resource/s
2. Setting a custom scheme specifically for Flutter should be highlighted in this package, otherwise, redirecting URIs feels like broken if it's not opening the app
3. Create example integration for bank institutions with OAuth

Nonetheless, thanks for creating this package!

[joshuadeguzman]

@jorgefspereira, we can collaborate and I can work with you on this and submit a PR.

[jorgefspereira]

Hi @joshuadeguzman, these are three great improvements that will help newcomers to integrate this package. I appreciate your help on this...feel free to PR this changes 😃 thank you

[joshuadeguzman]

Happy to! Feel free to assign the issue to me.