Replaced document exec Command ("copy"); #16604

gmarav05 wants to merge 2 commits intoistio:masteristio/istio.io:masterfrom

gmarav05:Replace-document.execCommand('copy')-with-navigator.clipboard.writeText(str)-for-modern,-secure-clipboard-handling-gmarav05/istio.io:Replace-document.execCommand('copy')-with-navigator.clipboard.writeText(str)-for-modern,-secure-clipboard-handling-Copy head branch name to clipboard