[Fix] Add Clarification around no loading state - Issue 614

[dtroupe-plaid]

Summary

• Adds clarifying comments about the use of noLoadingState in LinkTokenConfiguration type.
• Updates readme to state that noLoadingState is required.

Motivation

Flagged as an issue

📝 Checklist

• I have performed a self-review of my own code.
• I have optimized code readability (class/variable names, straight forward logic paths, short clarifying docs,...).

💚 Testing

• I have manually tested my changes.

Documentation

Select one:

• I have added relevant documentation for my changes.
• This PR does not result in any developer-facing changes.