Margins in email composer are smaller than in email clients

Margins between paragraphs are very small in the email composer:


But comparatively large when displayed in an email client:


I think we should set the CSS for the Quill text editor component so that paragraph margins are larger. Then, ideally, when sending an email through the email composer, the CSS that it uses for margins would be embedded in the HTML output that is sent through SendGrid, to make sure everything is consistent.