Require Node.js 8, add TypeScript definition

.travis.yml

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

index.d.ts

@@ -0,0 +1,34 @@
+import words = require('./words.json');
+
+declare const superb: {
+	/**
+	All the words in alphabetical order.
+
+	@example
+	```
+	import superb = require('superb');
+
+	superb.all;
+	//=> ['ace', 'amazing', …]
+	```
+	*/
+	readonly all: Readonly<typeof words>;
+
+	/**
+	Random word.
+
+	@example
+	```
+	import superb = require('superb');
+
+	superb.random();
+	//=> 'legendary'
+
+	superb.random();
+	//=> 'awesome'
+	```
+	*/
+	random(): string;
+};
+
+export = superb;

index.test-d.ts

@@ -0,0 +1,5 @@
+import {expectType} from 'tsd';
+import superb = require('.');
+
+expectType<readonly string[]>(superb.all);
+expectType<string>(superb.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",
 		"words.json"
 	],
 	"keywords": [
@@ -29,10 +30,16 @@
 		"random"
 	],
 	"dependencies": {
-		"unique-random-array": "^1.0.0"
+		"unique-random-array": "^2.0.0"
 	},
 	"devDependencies": {
-		"ava": "*",
-		"xo": "*"
+		"ava": "^1.4.1",
+		"tsd": "^0.7.2",
+		"xo": "^0.24.0"
+	},
+	"tsd": {
+		"compilerOptions": {
+			"resolveJsonModule": true
+		}
 	}
 }

readme.md

@@ -26,14 +26,14 @@ superb.random();
 //=> 'awesome'
 
 superb.all;
-//=> ['superb', 'legendary', …]
+//=> ['ace', 'amazing', …]
 ```
 
 ## API
 
 ### .all
 
-Type: `Array`
+Type: `string[]`
 
 All the words in alphabetical order.