Add test file for TS

I haven't added any tooling for this test. To check it, Typescript
needs to be installed. Then run:
    tsc --noEmit ./tests/test.ts

tests/test.ts

@@ -0,0 +1,41 @@
+import Pjax = require("../index");
+
+let options: Pjax.IOptions = {
+  elements: "a.pjax, form.pjax",
+  selectors: ["div.pjax"],
+  switches: {
+    "a.pjax": (oldEl, newEl) => {
+      oldEl.parentNode.replaceChild(newEl, oldEl);
+      this.onSwitch();
+    },
+    "form.pjax": Pjax.switches.innerHTML
+  },
+  switchesOptions: {},
+  history: true,
+  analytics: false,
+  scrollTo: 1,
+  scrollRestoration: false,
+  cacheBust: false,
+  debug: true,
+  timeout: 60000,
+  currentUrlFullReload: true
+};
+
+options.analytics = () => {};
+options.scrollTo = [1, 1];
+options.scrollTo = false;
+
+if (Pjax.isSupported()) {
+  delete options.switchesOptions;
+  const pjax = new Pjax(options);
+
+  pjax.reload();
+  pjax.loadUrl("https://example.org", options);
+
+  pjax._handleResponse = pjax.handleResponse;
+  pjax.handleResponse = (requestText: string, request: XMLHttpRequest, href: string) => {
+    pjax.abortRequest(request);
+
+    return pjax._handleResponse(requestText, request, href);
+  }
+}