fix: package.json module path

Author: esfox

package.json

@@ -12,6 +12,7 @@
     "all": "npm run clean && npm run build && npm test && npm run test:mutation",
     "clean": "rimraf \"+(test|src)/*.+(js|map|tsbuildinfo|d.ts)\" dist",
     "build": "tsc -b && tsc -p src --outDir dist/esm --module esnext --target esnext",
+    "prepare": "npm run build",
     "test": "mocha",
     "test:mutation": "stryker run",
     "version": "npm run generate-changelog",