chrome.runtime.onInstalled.addListener(function () {
    chrome.declarativeContent.onPageChanged.removeRules(undefined, function () {
        chrome.declarativeContent.onPageChanged.addRules([{
            conditions: [
                new chrome.declarativeContent.PageStateMatcher({
                    pageUrl: {
                        hostContains: 'vocabulary.com',
                        urlMatches: 'dictionary/.+$'
                    },
                })
            ],
            actions: [new chrome.declarativeContent.ShowPageAction()]
        }]);
    });
});