function detectFeed(event) {

	// force application/rss+xml to text/xml so the browser displays it instead of downloading

	var isfeed = false;

	for (var header of event.responseHeaders) {
	    if (header.name.toLowerCase() == "content-type") {
			header.value = header.value.replace(/application\/(rss|atom)\+xml/,'text/xml');
			isfeed = true;
			break;
	    }
	}

	if (isfeed) {

		for (var i = 0; i < event.responseHeaders.length; i++) {
		    if (event.responseHeaders[i].name.toLowerCase() == "cache-control") {
				event.responseHeaders.splice(i, 1);
				break;
		    }
		}

		// don't cache requests we modified
		// otherwise on reload the content-type won't be modified again
		event.responseHeaders.push({ name : "Cache-Control", value : "no-cache, no-store, must-revalidate" });

	}

    return {
        responseHeaders: event.responseHeaders
    };

}

const browser = window.browser || window.chrome;

browser.webRequest.onHeadersReceived.addListener(
    detectFeed,
    { urls: ["<all_urls>"], types: ["main_frame"] },
    ["blocking", "responseHeaders"]
)