Updates the default runner debian image sha to the multi-arch image instead of amd64-only. Also symlinks .containerignore -> .dockerignore since docker refuses to read .containerignore. With that one can build and push multi-arch, like so: ``` docker buildx create --name tranquil-multiarch --driver docker-container --bootstrap docker buildx build \ --builder tranquil-multiarch \ --platform linux/amd64,linux/arm64 \ -t atcr.io/tranquil.farm/tranquil-pds:0.6.7 \ --push \ . docker buildx imagetools create \ -t atcr.io/tranquil.farm/tranquil-pds:latest \ atcr.io/tranquil.farm/tranquil-pds:0.6.7 ``` if one were so inclined, that is.