Updated style configurations, readme, and added a linting script.

Signed-off-by: Nick Campbell <nicholas.j.campbell@gmail.com>

.editorconfig

@@ -0,0 +1,5 @@
+root = true
+
+[*.{js}]
+indent_style = tab
+indent_size = 2

.eslintrc

@@ -1,28 +1,26 @@
 {
 	"extends": ["standard", "prettier", "prettier/standard"],
 	"parserOptions": {
-		"ecmaVersion": "2017",
-		"sourceType": "module"
+		"ecmaVersion": 2018
 	},
 	"globals": {
-		"define": true,
-		"after": true,
-		"afterEach": true,
-		"before": true,
-		"beforeEach": true,
-		"describe": true,
-		"expect": true,
-		"it": true
+		"define": "readonly"
 	},
 	"env": {
 		"browser": true,
+		"es6": true,
 		"node": true,
 		"jest/globals": true
 	},
 	"plugins": ["prettier", "standard", "jest"],
 	"rules": {
 		"space-before-function-paren": 0,
 		"new-cap": 0,
-		"prettier/prettier": 2
+		"prettier/prettier": 2,
+		"jest/no-disabled-tests": 1,
+		"jest/no-focused-tests": 2,
+		"jest/no-identical-title": 2,
+		"jest/prefer-to-have-length": 1,
+		"jest/valid-expect": 2
 	}
 }

.prettierrc

@@ -1,4 +1,6 @@
 {
-	"useTabs": true,
-	"singleQuote": true
+	"arrowParens": "avoid",
+	"singleQuote": true,
+	"trailingComma": "none",
+	"useTabs": true
 }

README.md

@@ -4,7 +4,7 @@
 [![Build Status](https://badgen.net/github/status/kelektiv/node-cron?icon=github)](https://badgen.net/github/status/kelektiv/node-cron)
 [![Build Checks](https://badgen.net/github/checks/kelektiv/node-cron?icon=github)](https://badgen.net/github/checks/kelektiv/node-cron)
 [![Dependency Status](https://badgen.net/david/dep/kelektiv/node-cron)](https://badgen.net/david/dev/kelektiv/node-cron)
-[![Code Coverage](https://badgen.net/codecov/c/github/kelektiv/node-cron?icon=codecov)](https://badgen.net/codecov/c/igithub/kelektiv/node-cron)
+[![Code Coverage](https://badgen.net/codecov/c/github/kelektiv/node-cron?icon=codecov)](https://badgen.net/codecov/c/github/kelektiv/node-cron)
 [![Known Vulnerabilities](https://snyk.io/test/github/kelektiv/node-cron/badge.svg)](https://snyk.io/test/github/kelektiv/node-cron)
 [![Minified size](https://badgen.net/bundlephobia/min/cron)](https://badgen.net/bundlephobia/min/cron)
 [![Minzipped size](https://badgen.net/bundlephobia/minzip/cron)](https://badgen.net/bundlephobia/minzip/cron)

package.json

@@ -12,6 +12,7 @@
 	},
 	"main": "lib/cron",
 	"scripts": {
+		"lint": "eslint {lib,tests}/*.js",
 		"test": "jest --coverage"
 	},
 	"dependencies": {