chore(jest): setup jest with esm

Running jest without babel.

Using [email protected] because of the following error:

```
TypeError: Jest: a transform must export a `process` function.
```

See kenotron/esm-jest#5 (comment)

jest.config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  transform: {
+    "\\.m?jsx?$": "esm"
+  },
+  moduleNameMapper: {
+    "^anotherRoot/(.*)$": "<rootDir>/lib/anotherRoot/$1"
+  },
+  transformIgnorePatterns: []
+};

package.json

@@ -8,7 +8,7 @@
     "lint:precommit": "echo \"No precommit linting yet\" && exit 0",
     "test:precommit": "npm test",
     "pretty": "npx prettier --write '**/*.{tsx,ts,js,jsx,json,css,scss,md}'",
-    "test": "echo \"No test specified yet\" && exit 0"
+    "test": "npx jest --runInBand --no-cache --config jest.config.js"
   },
   "lint-staged": {
     "**/*.{tsx,ts,js,jsx,json,css,scss,md}": [
@@ -24,7 +24,9 @@
   "author": "Christophe Rosset <[email protected]> (http://labs.topheman.com/)",
   "license": "MIT",
   "devDependencies": {
+    "esm": "3.1.0",
     "husky": "^1.3.1",
+    "jest": "^24.8.0",
     "lint-staged": "^8.1.0",
     "prettier": "1.18.2",
     "serve": "^11.1.0"

src/js/logic.js

@@ -27,7 +27,7 @@ function createStore(initialReducer, initialState = {}, enhancer) {
   };
 }
 
-function reducer(state = 0, action) {
+export function reducer(state = 0, action) {
   switch (action.type) {
     case "ADD":
       return state + 1;

src/js/logic.test.js

@@ -0,0 +1,7 @@
+import { reducer } from "./logic";
+
+describe("logic.reducer", () => {
+  it("default state - ADD function should resolve to 1", () => {
+    expect(reducer(undefined, { type: "ADD" })).toBe(1);
+  });
+});