Updated examples.json with context-menu-demo
Updated examples.json with context-menu-demo

evolighting/webextensions-examples,evolighting/webextensions-examples,matthewjwein/webextensions-examples,matthewjwein/webextensions-examples,matthewjwein/webextensions-examples,anaran/webextensions-examples,mdn/webextensions-examples,anaran/webextensions-examples,mdn/webextensions-examples,evolighting/webextensions-examples,mdn/webextensions-examples