Fix types reference in package.json

Author: koddsson

package.json

@@ -4,7 +4,7 @@
   "description": "Attach files via drag and drop or file input.",
   "main": "dist/index.umd.js",
   "module": "dist/index.js",
-  "types": "dist/index.d.ts",
+  "types": "dist/file-attachment-element.d.ts",
   "license": "MIT",
   "repository": "github/file-attachment-element",
   "files": [