build(tests): Adds jest to run tests

Milestone: none
Signed-off-by: Alix von Schirp <github@avonschirp.bootmedia.de>

tests/index.spec.ts

@@ -0,0 +1,11 @@
+import Pushover from "../src";
+
+test("Pushover is exported", () => {
+  expect(Pushover).toBeDefined();
+  expect(Pushover).toBeInstanceOf(Object);
+});
+
+test("Pushover has expected functions", () => {
+  expect(Pushover).toHaveProperty("prototype.constructor");
+  expect(Pushover).toHaveProperty("prototype.send");
+});