Add WebExtensions Tabs.Tab.successorTabId (#5875)
Add WebExtensions Tabs.Tab.successorTabId (#5875)

Thanks @vinyldarkscratch , everything looks good now and I have merged
chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data