Update package.json

fix: fixed main file path

src/headless/package.json

@@ -5,7 +5,7 @@
   "author": "cmrd Senya <senya@riseup.net>",
   "homepage": "https://conversejs.org",
   "license": "MPL-2.0",
-  "main": "dist/converse-headless.js",
+  "main": "dist/converse-headless.min.js",
   "files": [
     "**/*.js",
     "templates/*"