[Minor] Add some standard types for .p7s extension

lualib/lua_mime_types.lua

@@ -358,9 +358,9 @@ exports.full_extensions_map = {
     {"p12", "application/x-pkcs12"},
     {"p7b", "application/x-pkcs7-certificates"},
     {"p7c", "application/pkcs7-mime"},
-    {"p7m", "application/pkcs7-mime"},
+    {"p7m", "application/pkcs7-mime", "application/x-pkcs7-mime"},
     {"p7r", "application/x-pkcs7-certreqresp"},
-    {"p7s", {"application/pkcs7-signature", "text/plain"}},
+    {"p7s", {"application/pkcs7-signature", "application/x-pkcs7-signature", "text/plain"}},
     {"pbm", "image/x-portable-bitmap"},
     {"pcast", "application/x-podcast"},
     {"pct", "image/pict"},