Update Helm chart with v0.20.0

[mloiseleur]

Update Helm chart to latest version

cc @stevehipwell

[johnjeffers]

While we wait for the helm chart for 0.20.0 to be released, is it safe to use the 0.19.0 chart and override image.tag to use 0.20.0? Or are there changes in 0.20.0 that will require helm chart changes, CRD updates, etc?