Enable multiarch builds

The current v0.2.0 are not multi-arch and are amd64 specific.

Would be great to be able to run it all around!

I've now built a multiarch image for arm64 and armv7 and tested it on a cluster. It works wonders so we just need to enable whatever CI to push them out.

No need to set GOARCH in the Dockerfile even.

it will be nice to create a script we can call from the makefile

kube-network-policies/Makefile

Lines 41 to 43 in 081163b

    
           image-build: 
        
           # docker buildx build --platform=${PLATFORMS} $(OUTPUT) --progress=$(PROGRESS) -t ${IMAGE} --pull $(EXTRA_BUILD_OPT) . 
        
           	docker build . -t ${IMAGE}

Then I can work in automating it, @vaskozl is this something you want to help?

	image-build:
	# docker buildx build --platform=${PLATFORMS} $(OUTPUT) --progress=$(PROGRESS) -t ${IMAGE} --pull $(EXTRA_BUILD_OPT) .
	docker build . -t ${IMAGE}