Require Node.js 8, add TypeScript definition (#4)

.travis.yml

@@ -1,5 +1,5 @@
 language: node_js
 node_js:
+  - '12'
   - '10'
   - '8'
-  - '6'

index.d.ts

@@ -0,0 +1,31 @@
+import supervillainsJson = require('./supervillains.json');
+
+declare const supervillains: {
+	/**
+	Supervillain names in alphabetical order.
+
+	@example
+	```
+	const supervillains = require('supervillains');
+
+	supervillains.all;
+	//=> ['Abattoir', 'Able Crown', …]
+	```
+	*/
+	readonly all: Readonly<typeof supervillainsJson>;
+
+	/**
+	Random supervillain name.
+
+	@example
+	```
+	const supervillains = require('supervillains');
+
+	supervillains.random();
+	//=> 'Mud Pack'
+	```
+	*/
+	random(): string;
+};
+
+export = supervillains;

index.test-d.ts

@@ -0,0 +1,5 @@
+import {expectType} from 'tsd';
+import supervillains = require('.');
+
+expectType<readonly string[]>(supervillains.all);
+expectType<string>(supervillains.random());

package.json

@@ -10,13 +10,14 @@
 		"url": "sindresorhus.com"
 	},
 	"engines": {
-		"node": ">=6"
+		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
 		"index.js",
+		"index.d.ts",
 		"supervillains.json"
 	],
 	"keywords": [
@@ -35,10 +36,16 @@
 		"comics"
 	],
 	"dependencies": {
-		"unique-random-array": "^1.0.0"
+		"unique-random-array": "^2.0.0"
 	},
 	"devDependencies": {
-		"ava": "^1.2.1",
+		"ava": "^1.4.1",
+		"tsd": "^0.7.2",
 		"xo": "^0.24.0"
+	},
+	"tsd": {
+		"compilerOptions": {
+			"resolveJsonModule": true
+		}
 	}
 }

readme.md

@@ -19,6 +19,9 @@ $ npm install supervillains
 ```js
 const supervillains = require('supervillains');
 
+supervillains.all;
+//=> ['Abattoir', 'Able Crown', …]
+
 supervillains.random();
 //=> 'Mud Pack'
 ```
@@ -28,7 +31,7 @@ supervillains.random();
 
 ### .all
 
-Type: `Array`
+Type: `string[]`
 
 Supervillain names in alphabetical order.