git: Use vim-mergetool for merge conflicts

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

git/.gitconfig

@@ -11,5 +11,9 @@
 	smtpserver = /usr/bin/msmtp
 [http]
 	sslVerify = false
-[alias]
-	conflicted = !vim +Conflicted
+[merge]
+	tool = vim_mergetool
+	conflictstyle=diff3
+[mergetool "vim_mergetool"]
+	cmd = nvim -f -c "MergetoolStart" "$MERGED" "$BASE" "$LOCAL" "$REMOTE"
+	trustExitCode = true