add reference to RFC 3676 to standards.md

RFC 3676 is understood for incoming messages
and used for outgoing messages.

standards.md

@@ -6,6 +6,7 @@ Tasks                            | Standards
 ---------------------------------|---------------------------------------------
 Transport                        | IMAP v4 ([RFC 3501](https://tools.ietf.org/html/rfc3501)), SMTP ([RFC 5321](https://tools.ietf.org/html/rfc5321)) and Internet Message Format (IMF, [RFC 5322](https://tools.ietf.org/html/rfc5322))
 Embedded media                   | MIME Document Series ([RFC 2045](https://tools.ietf.org/html/rfc2045), [RFC 2046](https://tools.ietf.org/html/rfc2046)), Content-Disposition Header ([RFC 2183](https://tools.ietf.org/html/rfc2183)), Multipart/Related ([RFC 2387](https://tools.ietf.org/html/rfc2387))
+Text and Quote encoding          | Fixed, Flowed ([RFC 3676](https://tools.ietf.org/html/rfc3676))
 Filename encoding                | Encoded Words ([RFC 2047](https://tools.ietf.org/html/rfc2047)), Encoded Word Extensions ([RFC 2231](https://tools.ietf.org/html/rfc2231))
 Identify server folders          | IMAP LIST Extension ([RFC 6154](https://tools.ietf.org/html/rfc6154))
 Push                             | IMAP IDLE ([RFC 2177](https://tools.ietf.org/html/rfc2177))