add arm64 image and/or add affinity capabilities to helm chart

[MatthewStockdale]

I would like to run silence-operator in my cluster, but since I run mixed arm64/amd64 nodes, if silence-operator attempts to launch on a arm64 node it fails.

arm64 builds would be the best outcome, but adding the ability to pass in node affinity via the helm chart would allow me to restrict to amd64 nodes.

[QuentinBisson]

With release 0.17.0, you can now use node affinities. Adding ARM support is in the pipe but will take longer.

Make sure to check out the changelog