rtl: Extend documentation with RTL user guide

[rascmatt]

Extend the online documentation with a guide on how to use the RTL generator and set up the generated Chisel project.

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For the docker-based RTL tests we currently prepare and use a docker image which provides the necessary toolchains for instruction tests and benchmarking:

openvadl/docker/rtl/test-base/Dockerfile

Lines 1 to 4 in e63edec

	FROM ghcr.io/openvadl/merged-toolchain@sha256:2ceaf5369996a5f3db0e0bb8e16ae5fe53003d6ac180bd9e60a9ced954f99a9a AS toolchains
	FROM ghcr.io/openvadl/firtool@sha256:84c7b84322068a9b800c908a13656a6d756a507751230dad1c99c38b96bad335 AS firtool
	FROM ubuntu:22.04 AS build

openvadl/.github/workflows/build-rtl-test-base.yml

Line 1 in e63edec

name: Build RTL test base image

In addition I added a devcontainer configuration to the generated RTL scala project to be used with IntelliJ. See #790