feat: Add TypeScript definitions

package.json

@@ -50,14 +50,15 @@
     "madge": "5.0.1",
     "mailgun.js": "3.5.9",
     "nyc": "15.1.0",
-    "semantic-release": "21.0.2"
+    "semantic-release": "21.0.2",
+    "typescript": "^5.2.2"
   },
   "engines": {
     "node": ">=12"
   },
   "scripts": {
     "build:watch": "babel src --out-dir lib --source-maps --watch",
-    "build": "babel src --out-dir lib --source-maps",
+    "build": "babel src --out-dir lib --source-maps && tsc",
     "lint": "eslint '{src,spec,demo}/**/*.js' 'release.config.js'",
     "lint:fix": "eslint '{src,spec,demo}/**/*.js' --fix",
     "madge": "node_modules/.bin/madge ./src $npm_config_arg",

tsconfig.json

@@ -0,0 +1,23 @@
+{
+  // Change this to match your project
+  "include": [
+    "src/**/*"
+  ],
+  "compilerOptions": {
+    // Tells TypeScript to read JS files, as
+    // normally they are ignored as source files
+    "allowJs": true,
+    // Generate d.ts files
+    "declaration": true,
+    // This compiler run should
+    // only output d.ts files
+    "emitDeclarationOnly": true,
+    // Types should go into this directory.
+    // Removing this would place the .d.ts files
+    // next to the .js files
+    "outDir": "lib",
+    // go to js file when using IDE functions like
+    // "Go to Definition" in VSCode
+    "declarationMap": true
+  }
+}