Support Modern Remote Chrome (#71)

Starting in version 66, Chrome DevTools requires the host header to be
“localhost” or an IP address. Work around this by setting the header to
“lcoalhost” when fetching the version endpoint.

library/Pdfexport/HeadlessChrome.php

@@ -755,7 +755,22 @@ public function getVersion()
     protected function jsonVersion($host, $port)
     {
         $client = new \GuzzleHttp\Client();
-        $response = $client->request('GET', sprintf('http://%s:%s/json/version', $host, $port));
+
+        try {
+            $response = $client->request('GET', sprintf('http://%s:%s/json/version', $host, $port));
+        } catch (\GuzzleHttp\Exception\ServerException $e) {
+            // Check if we've run into the host header security change, and re-run the request with no host header.
+            // ref: https://issues.chromium.org/issues/40090537
+            if (strstr($e->getMessage(), 'Host header is specified and is not an IP address or localhost.')) {
+                $response = $client->request(
+                    'GET',
+                    sprintf('http://%s:%s/json/version', $host, $port),
+                    ['headers' => ['Host' => null]]
+                );
+            } else {
+                throw $e;
+            }
+        }
 
         if ($response->getStatusCode() !== 200) {
             return false;