Update gitcommit.snippets: add Co-authored-by snippet

Author: jiangyinzuo

UltiSnips/gitcommit.snippets

@@ -71,6 +71,10 @@ build(${1:scope}): ${2:title}
 ${0:${VISUAL}}
 endsnippet
 
+snippet Co-authored-by "Co-authored-by:"
+Co-authored-by: ${1:Author Name} <${2:Email}>
+endsnippet
+
 snippet sign "Signature"
 -------------------------------------------------------------------------------
 ${1:Company Name}