Add eslint command to yarn (#1324)

* Adds a `yarn lint` command that runs `eslint`
* Starts work on #1245

.eslintrc.js

@@ -0,0 +1,17 @@
+module.exports = {
+    "env": {
+        "browser": true,
+        "es6": true
+    },
+    "extends": "eslint:recommended",
+    "globals": {
+        "Atomics": "readonly",
+        "SharedArrayBuffer": "readonly"
+    },
+    "parserOptions": {
+        "ecmaVersion": 2018,
+        "sourceType": "module"
+    },
+    "rules": {
+    }
+};