docs(chart_tips_and_tricks): explain resource-policy.
docs(chart_tips_and_tricks): explain resource-policy.

This adds a short explanation of the resource policy annotation.

Closes #1880

adamreese/deployment-manager,bacongobbler/helm,technosophos/deployment-manager,appscode/helm,yan234280533/helm,iamzhout/helm,FengyunPan/helm,technosophos/deployment-manager,bacongobbler/helm,iamzhout/helm,appscode/helm,helm/helm,adamreese/helm,adamreese/helm,SlickNik/helm,FengyunPan/helm,technosophos/k8s-helm,michelleN/deployment-manager,adamreese/deployment-manager,thomastaylor312/helm,adamreese/deployment-manager,eicnix/helm,technosophos/deployment-manager,adamreese/deployment-manager,technosophos/deployment-manager,rbwsam/helm,kdada/helm,michelleN/deployment-manager,michelleN/deployment-manager,fibonacci1729/helm,sushilkm/helm,technosophos/k8s-helm,flynnduism/helm,helm/helm,michelleN/deployment-manager,kdada/helm,jascott1/helm,eicnix/helm,fibonacci1729/helm,qwangrepos/helm,adamreese/deployment-manager,sushilkm/helm,technosophos/deployment-manager,flynnduism/helm,jascott1/helm,SlickNik/helm,qwangrepos/helm,rbwsam/helm,thomastaylor312/helm,yan234280533/helm