feat: add ts typedefs

index.d.ts

@@ -0,0 +1,16 @@
+export type Scalar = number | string | boolean | bigint | null | undefined;
+export interface Err<Code extends Scalar, Ext extends Object> extends Error, Ext {
+  code: Code
+}
+
+interface CreateError {
+  <Code extends Scalar, Ext extends Object> (
+    reason:string|Error,
+    code:Code,
+    ext:Ext
+  ):Err<Code, Ext>
+  <Code extends Scalar> (reason:string|Error, code:Code):Err<Code, {}>
+}
+
+declare var createError:CreateError
+exports = createError

package.json

@@ -3,6 +3,7 @@
   "version": "2.0.3",
   "description": "Create an error with a code",
   "main": "index.js",
+  "types": "index.d.ts",
   "scripts": {
     "lint": "eslint '{*.js,test/**/*.js}' --ignore-pattern *.umd.js",
     "test": "mocha --bail",