This should bring in a few styling improvements.

Acceptance Criteria:

• Use leafygreen input component for connection form inputs https://github.com/mongodb/leafygreen-ui/tree/master/packages/text-input 
• Use leafygreen modal component for the connection form modal https://github.com/mongodb/leafygreen-ui/tree/master/packages/modal 
• The text input should reflect errors correctly
• The components should be responsive with vscode color themes (light and dark)