chore(jest): run tests with jest (#2754)

Experimentally run `npx jest` to run our tests with jest.

Author: JoelEinbinder

jest.config.json

@@ -0,0 +1,5 @@
+{
+  "runner": "./jest-runner.js",
+  "rootDir": "./test/",
+  "testMatch":  ["**/?(*.)spec.[jt]s"]
+}