add: git send-email and git credential helper

.config/git/config

@@ -16,8 +16,18 @@
 [alias]
 	dt = difftool
     d = diff
+    b = branch -vv
 [merge]
 	tool = vimdiff
 	conflictstyle = diff3
 [mergetool]
     prompt = false
+[credential]
+	helper = /usr/bin/pass-git-helper
+[format]
+	signOff = yes
+[sendemail]
+	smtpserver = mail.serguzim.me
+	smtpuser = tobias@msrg.cc
+	smtpencryption = tls
+	smtpserverport = 587

.config/pass-git-helper/git-pass-mapping.ini

@@ -0,0 +1,2 @@
+[mail.serguzim.me:587]
+target=mail/${username}