chore(ci): add es-check dev dep (#29)

* chore(build): add es-check

since this lib isn't transpiled we should ensure adherence to our min supported JS vintage

* chore(ci): add es check step

.circleci/config.yml

@@ -16,6 +16,7 @@ jobs:
     steps:
       - checkout
       - run: yarn install
+      - run: yarn escheck
       - run: yarn test
       - persist_to_workspace:
           root: .

package.json

@@ -4,7 +4,8 @@
   "description": "Canadian SIN (Social Insurance Number) parser and generator",
   "main": "social-insurance-number.js",
   "scripts": {
-    "test": "jest"
+    "test": "jest",
+    "escheck": "es-check es5 social-insurance-number.js"
   },
   "repository": {
     "type": "git",
@@ -18,6 +19,7 @@
   ],
   "license": "MIT",
   "devDependencies": {
+    "es-check": "^5.2.3",
     "jest": "^24.5.0",
     "semantic-release": "^15.13.3"
   }