Small fixups in eslintrc

Remove duplicate key.
Enable jest env.

Author: Tony Joblin

.eslintrc.json

@@ -1,18 +1,15 @@
 {
   "env": {
       "es6": true,
-      "node": true
+      "node": true,
+      "jest": true
   },
   "extends": "eslint:recommended",
   "parserOptions": {
       "ecmaVersion": 2018,
       "sourceType": "module"
   },
   "rules": {
-      "indent": [
-          "error",
-          2
-      ],
       "linebreak-style": [
           "error",
           "unix"