Add textproc/py-RTFDE: Library for extracting HTML content from RTF encapsulated HTML

RTFDE is a python3 library for extracting encapsulated HTML & plain
text content from the RTF bodies of .msg files.

De-encapsulation enables previously encapsulated HTML and plain
text content to be extracted and rendered as HTML and plain text
instead of the encapsulating RTF content. After de-encapsulation,
the HTML and plain text should differ only minimally from the
original HTML or plain text content.

WWW: https://github.com/seamustuohy/RTFDE

PR: 265764