@Override
        @NonNull
        public Response intercept(final Interceptor.Chain chain) throws IOException {
            final Request request = chain.request().newBuilder()
                    .header("Accept-Charset", "utf-8,iso-8859-1;q=0.8,utf-16;q=0.8,*;q=0.7")
                    .header("Accept-Language", "en-US,*;q=0.9")
                    .header("X-Requested-With", "XMLHttpRequest")
                    .header("User-Agent", USER_AGENT)
                    .build();
            return chain.proceed(request);
        }
Add headers to HTTP request.

@param request   the request builder to add headers to
@param headers   the headers to add (in addition to the standard headers), can be null
@param cacheFile if non-null, the file to take ETag and If-Modified-Since information from
main/src/main/java/cgeo/geocaching/network/Network.java