Merge pull request #1 from Robin-Hoodie/feat/package-json-main

feat: add package.json#main to fix usage in jest

Author: junderw

package.json

@@ -10,6 +10,7 @@
     "type": "git",
     "url": "https://github.com/bitcoinjs/uint8array-tools.git"
   },
+  "main": "./src/cjs/index.cjs",
   "exports": {
     "node": {
       "module": "./src/mjs/index.js",