Update use_cases_navigation.html
Update use_cases_navigation.html

Added link to client headers page
ted-spence-avalara/developer-dot,bob-erdman/developer-dot,bob-erdman/developer-dot,ted-spence-avalara/developer-dot,bob-erdman/developer-dot,ted-spence-avalara/developer-dot,ted-spence-avalara/developer-dot,ted-spence-avalara/developer-dot,bob-erdman/developer-dot,bob-erdman/developer-dot