package.json: Point main/module/types to dist/

See also: lit#30 (comment)

Author: tony

package.json

@@ -2,8 +2,9 @@
   "name": "lit-element-starter-ts",
   "version": "0.0.0",
   "description": "A simple web component",
-  "main": "my-element.js",
-  "module": "my-element.js",
+  "main": "./dist/my-element.js",
+  "module": "./dist/my-element.js",
+  "types": "./dist/my-element.d.ts",
   "type": "module",
   "scripts": {
     "build": "tsc",