…sx (#140)

- Build a docker image and use it in all subsequent jobs. Speeds up CI by about 30%
- Build all bitstreams using the `oss-cad-suite` binaries instead of yowasp, as it completes faster.
- Add another (non-dockerized) build which runs a `pdm install && pdm dsp build` and check it completes successfully on linux, windows and mac. This will form part of the getting started tutorial as it is easy to run on every platform and uses yowasp.
- For SoC bitstream building (requires a lot more dependencies) users will have the option of installing the toolchains natively or just running the jobs inside the docker container using a new `scripts/docker.sh` script. This will work fine on osx and linux, but windows might require WSL

* docs: add quickstart sections for all SKUs
* docs: fix gitignore

Add a simple framework for writing beamracing video cores, where the audio inputs are already correctly synchronized into the pixel clock, making it easy to use the audio inputs to tweak the beamracing pattern.

Most of these are directly translated from https://vga-playground.com/ - with some minor edits so that the audio inputs also do something to the patterns.

Add a simple DWO core, and an example bitstream that instantiates 16 of them sharing a single multiplier. This core is an interesting way to produce sine waves without needing a LUT.