Upgrade to SPFx v1.20.0#1455

Adam-it merged 5 commits intopnp:mainpnp/sp-dev-fx-extensions:mainfrom

NishkalankBezawada:feature/Upgrade-AppCustomizer-MachineTranslations-v1.20.0NishkalankBezawada/sp-dev-fx-extensions:feature/Upgrade-AppCustomizer-MachineTranslations-v1.20.0Copy head branch name to clipboard