Is there a way to use residual NN in Mathematica that is built-in that I'm missing? Looking at how Mathematica implements residual nets in the NetModel, it is just a NetGraph. Hence I propose a simple code for residual Nets in Mathematica which can be easily used on NetChain statements.
NetResidual[layers_] := NetGraph[{TotalLayer[], layers}, {
NetPort["Input"] -> 1,
NetPort["Input"] -> 2 -> 1 -> NetPort["Output"]
}]