VF Chatbot: Implement changes as per feedback

[bhushan-ebi]

As per the feedback below implement changes:

• FAB location needs to be equidistant from bottom and right
• Modal design to update to fullscreen in mobile and should be fixed
• Reduce font size for disclaimer banner
• Disclaimer banner to show per session
• Adjust height of the modal as per updates from Ux recommendation
• Add border/shadow as per Ux recommendation
• Add space between text and 'Contact Us' prompt in assistant response
• Remove white border across Send button
• Check and fix button space between feedback options in the feedback form.
• Space between horizontal rule and domain text to be increased inside sources
• Make it configurable to minimize chat when user goes to otherp age
• Add blank page for accessibility testing