Add html and text properties to support multipart/alternative email bodies easily #3
Description
I notice Plunk's API and @plunk/node only support a body property.
It'd be nice if they accepted html and text properties that, such that if both are specified simultaneously, a multipart/alternative email body is used (see below).
There are good reasons to include plaintext in addition to the HTML, described here React Email's site.
It should be easy to add this too, and wouldn't require a breaking version bump, until you deprecate body someday.
Example
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="boundary_string"
--boundary_string
Content-Type: text/plain; charset=UTF-8
This is the plain text version of the email.
--boundary_string
Content-Type: text/html; charset=UTF-8
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Email Title</title>
</head>
<body>
<p>This is the HTML version of the email.</p>
</body>
</html>
--boundary_string--