Add Dockerfiles to the templates (#4637)
As requested [here](https://github.com/paritytech/polkadot-sdk/issues/3155#issuecomment-2126934939). The Dockerfiles are inspired by [this one](https://github.com/paritytech/polkadot-sdk/blob/aa32faae/docker/dockerfiles/polkadot/polkadot_builder.Dockerfile).