fix(body): Use css type selector for body background for outlook

[hillac]

Background color style in body doesn't work in outlook web. Outlook converts body to a div and strips styles. For example the stripe-welcome demo email doesn't render correctly in outlook, there is no background. Outlook seems to respect type selectors so adding a style tag with body type selector fixes this.

See https://github.com/resend/react-email/issues/662

May need to do this for every style applied to the body.