Uses curl to fetch k6 binary to solve github redirect issues

Makes use of `CURLOPT_FOLLOWLOCATION` to allow a redirect on github.

src/K6.php

@@ -80,10 +80,20 @@ public static function download(): void
         $url = sprintf(self::K6_URL, self::K6_VERSION, self::K6_VERSION, $os, $arch, $extension);
         $fileName = basename($url);
 
-        if (false === ($binary = file_get_contents($url))) {
+        $ch = curl_init();
+        curl_setopt($ch, CURLOPT_URL, $url);
+        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
+
+        $binary = curl_exec($ch);
+
+        if (false === $binary || 200 !== curl_getinfo($ch, CURLINFO_HTTP_CODE)) {
+            curl_close($ch);
             throw new RuntimeException('Unable to download k6 binary.');
         }
 
+        curl_close($ch);
+
         if (file_put_contents(self::BIN_DIR.$fileName, $binary) === false) {
             throw new RuntimeException('Unable to save k6 binary.');
         }