Update linting setup

* Update eslint to 7.x
* Move from `lint:js` to `lint`
* Use `npm-run-all` instead of `&&` in scripts
* Move `NODE_ENV` configuration into `.mocharc.js` (makes it so that
  `mocha test/some-file-test.js` works on its own)

.mocharc.js

@@ -0,0 +1,2 @@
+// set the NODE_ENV to test if not already set, NODE_ENV=test changes the default worker count to 1
+process.env.NODE_ENV = process.env.NODE_ENV || 'test';

package.json

@@ -19,8 +19,9 @@
   "author": "Tom Dale <tom@tomdale.net>",
   "main": "src/fastboot-app-server.js",
   "scripts": {
-    "lint:js": "eslint --cache .",
-    "test": "yarn lint:js && NODE_ENV=test mocha"
+    "lint": "eslint --cache .",
+    "test": "npm-run-all lint test:*",
+    "test:mocha": "mocha"
   },
   "dependencies": {
     "basic-auth": "^2.0.1",
@@ -32,10 +33,11 @@
   },
   "devDependencies": {
     "chai": "^4.1.0",
-    "eslint": "^6.8.0",
-    "eslint-plugin-mocha": "^6.3.0",
+    "eslint": "^7.12.0",
+    "eslint-plugin-mocha": "^8.0.0",
     "eslint-plugin-node": "^11.1.0",
     "mocha": "^8.2.0",
+    "npm-run-all": "^4.1.5",
     "release-it": "^14.2.0",
     "release-it-lerna-changelog": "^3.0.0",
     "request": "^2.81.0",