Add ESLint

.eslintrc.json

@@ -0,0 +1,20 @@
+{
+  "plugins": ["jest", "@typescript-eslint"],
+  "extends": ["plugin:github/es6"],
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": {
+    "ecmaVersion": 9,
+    "sourceType": "module"
+  },
+  "rules": {
+    "no-unused-vars": "off",
+    "eslint-comments/no-use": "off",
+    "import/no-namespace": "off",
+    "@typescript-eslint/no-unused-vars": "error"
+  },
+  "env": {
+    "node": true,
+    "es6": true,
+    "jest/globals": true
+  }
+}

package.json

@@ -6,6 +6,7 @@
     "build": "lerna run tsc",
     "format": "prettier --write packages/*/src/**/*.ts",
     "format-check": "prettier --check packages/*/src/**/*.ts",
+    "lint": "eslint packages/*/src/**/*.ts",
     "new-package": "scripts/create-package",
     "test": "jest"
   },
@@ -13,6 +14,10 @@
     "@types/jest": "^24.0.11",
     "@types/node": "^11.13.5",
     "@types/signale": "^1.2.1",
+    "@typescript-eslint/parser": "^1.9.0",
+    "eslint": "^5.16.0",
+    "eslint-plugin-github": "^2.0.0",
+    "eslint-plugin-jest": "^22.5.1",
     "jest": "^24.7.1",
     "jest-circus": "^24.7.1",
     "lerna": "^3.13.3",

tsconfig.json

@@ -1,6 +1,5 @@
 {
   "compilerOptions": {
-    "allowSyntheticDefaultImports": true,
     "module": "commonjs",
     "strict": true,
     "declaration": true,