Add linting and formatting

libraries/o-error/package.json

@@ -4,6 +4,7 @@
   "description": "Make custom error types that pass `instanceof` checks, have stack traces, support custom messages and properties, and can wrap causes (like VError).",
   "main": "index.js",
   "scripts": {
+    "lint": "eslint .",
     "test": "mocha --require test/support"
   },
   "author": "Overleaf (https://www.overleaf.com)",
@@ -11,6 +12,13 @@
   "repository": "github:overleaf/o-error",
   "devDependencies": {
     "chai": "^3.3.0",
-    "mocha": "^6.1.4"
+    "eslint": "^6.8.0",
+    "eslint-config-prettier": "^6.10.1",
+    "eslint-plugin-chai-expect": "^2.1.0",
+    "eslint-plugin-chai-friendly": "^0.5.0",
+    "eslint-plugin-mocha": "^6.3.0",
+    "eslint-plugin-prettier": "^3.1.3",
+    "mocha": "^7.1.1",
+    "prettier": "^2.0.2"
   }
 }