Merge pull request #5068 from ethereum-optimism/willc/module-fix

fix(atst): Fix module and main in package.json

.changeset/quiet-crews-leave.md

+---
+'@eth-optimism/atst': minor
+---
+
+Fix main and module in atst package.json

packages/atst/package.json

@@ -2,9 +2,9 @@
   "name": "@eth-optimism/atst",
   "version": "0.1.0",
   "type": "module",
-  "main": "dist/index.js",
+  "main": "dist/index.cjs",
   "types": "src/index.ts",
-  "module": "dist/index.cjs",
+  "module": "dist/index.js",
   "license": "MIT",
   "exports": {
     ".": {