vinitshahdeo#14 Add ESLint

Added [ESLint](https://eslint.org/) on this project.
Added scripts in package.json i.e. npm run test-lint should run lint tests.
[ESLint](https://eslint.org/)

.eslintrc.js

@@ -0,0 +1,18 @@
+module.exports = {
+    "env": {
+        "browser": true,
+        "es6": true,
+        "node": true
+    },
+    "extends": "eslint:recommended",
+    "globals": {
+        "Atomics": "readonly",
+        "SharedArrayBuffer": "readonly"
+    },
+    "parserOptions": {
+        "ecmaVersion": 2018,
+        "sourceType": "module"
+    },
+    "rules": {
+    }
+};

package.json

@@ -7,7 +7,8 @@
     "build": "mocha tests/pre.js && mocha tests/test.js && node src/tweet.js",
     "pretest": "mocha tests/pre.js",
     "test": "mocha tests/test.js",
-    "start": "node src/tweet.js"
+    "start": "node src/tweet.js",
+    "test-lint": "eslint --fix-dry-run --color --ignore-pattern node_modules/ ."
   },
   "repository": {
     "type": "git",
@@ -34,6 +35,7 @@
     "twitter": "1.7.1"
   },
   "devDependencies": {
-    "mocha": "^5.2.0"
+    "mocha": "^5.2.0",
+    "eslint": "^6.5.1"
   }
 }