Expand description
Renders a raw MIME message (an archived .eml, or any RFC 5322 message)
as human-readable Markdown, backing gmail render and gmail read -o markdown (#1513).
A sibling of crate::gmail::attachments, not an extension of
crate::gmail::raw_message’s line-oriented scanner: producing readable
text needs the same real MIME/multipart parsing attachments.rs already
pulls in (mail-parser), plus RFC 2047 encoded-word decoding of header
values — which that scanner’s own doc comment explicitly says it does not
attempt.