add tester

test/tester.js

+let Printer = require("./");
+const util = require('util');
+const fs = require('fs');
+const readFile = util.promisify(fs.readFile);
+
+(async () => {
+  let printer = new Printer();
+  // let page = await printer.render("test/samples/aurorae/index.html");
+  let pdf = await printer.pdf("https://s3.amazonaws.com/pagedmedia/samples/text.html");
+  // const html = await readFile("test/samples/aurorae/index.html", "utf-8");
+  // let pdf = await printer.pdf({ html });
+  // let html = await printer.html("test/samples/aurorae/index.html");
+  fs.writeFileSync(`output/out-${Date.now()}.pdf`, pdf);
+  return process.exit(0);
+})();