Documentation: Add minimal Mutt config for using Gmail

This patch provides a minimal configuration to set up Mutt for
submitting plain text patches using Gmail.

Signed-off-by: Eddie Kovsky <[e-mail]>
Reviewed-by: Darren Hart <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/email-clients.txt

···
 However, it's a good idea to set the "send_charset" to:
   set send_charset="us-ascii:utf-8"
 
+Mutt is highly customizable. Here is a minimum configuration to start
+using Mutt to send patches through Gmail:
+
+# .muttrc
+# ================  IMAP ====================
+set imap_user = '[e-mail]'
+set imap_pass = 'yourpassword'
+set spoolfile = imaps://imap.gmail.com/INBOX
+set folder = imaps://imap.gmail.com/
+set record="imaps://imap.gmail.com/[Gmail]/Sent Mail"
+set postponed="imaps://imap.gmail.com/[Gmail]/Drafts"
+set mbox="imaps://imap.gmail.com/[Gmail]/All Mail"
+
+# ================  SMTP  ====================
+set smtp_url = "smtp://[e-mail]:587/"
+set smtp_pass = $imap_pass
+set ssl_force_tls = yes # Require encrypted connection
+
+# ================  Composition  ====================
+set editor = `echo \$EDITOR`
+set edit_headers = yes  # See the headers when editing
+set charset = UTF-8     # value of $LANG; also fallback for send_charset
+# Sender, email address, and sign-off line must match
+unset use_domain        # because joe@localhost is just embarrassing
+set realname = "YOUR NAME"
+set from = "[e-mail]"
+set use_from = yes
+
+The Mutt docs have lots more information:
+    http://dev.mutt.org/trac/wiki/UseCases/Gmail
+    http://dev.mutt.org/doc/manual.html
+
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 Pine (TUI)