Convert examples/components/pageviewer.js to await/async (issue 14127)
Convert examples/components/pageviewer.js to await/async (issue 14127)

timvandermeij/pdf.js,mozilla/pdf.js,nawawi/pdf.js,macroplant/pdf.js,timvandermeij/pdf.js,Snuffleupagus/pdf.js,timvandermeij/pdf.js,mozilla/pdf.js,nawawi/pdf.js,showpad/mozilla-pdf.js,Shoobx/pdf.js,showpad/mozilla-pdf.js,Snuffleupagus/pdf.js,nawawi/pdf.js,mozilla/pdf.js,macroplant/pdf.js,macroplant/pdf.js,Shoobx/pdf.js,Snuffleupagus/pdf.js,Shoobx/pdf.js,showpad/mozilla-pdf.js