Fix exported extensions in package.json

clients/js/package.json

@@ -1,17 +1,17 @@
 {
   "name": "@solana-program/system",
-  "version": "0.1.2",
+  "version": "0.1.3",
   "description": "JavaScript client for the System program",
   "sideEffects": false,
-  "module": "./dist/src/index.mjs",
-  "main": "./dist/src/index.js",
+  "module": "./dist/src/index.js",
+  "main": "./dist/src/index.cjs",
   "types": "./dist/types/src/index.d.ts",
   "type": "module",
   "exports": {
     ".": {
       "types": "./dist/types/src/index.d.ts",
-      "import": "./dist/src/index.mjs",
-      "require": "./dist/src/index.js"
+      "import": "./dist/src/index.js",
+      "require": "./dist/src/index.cjs"
     }
   },
   "files": [

clients/js/tsup.config.ts

@@ -7,6 +7,7 @@ const SHARED_OPTIONS: Options = {
   entry: ['./src/index.ts'],
   inject: [path.resolve(__dirname, 'env-shim.ts')],
   outDir: './dist/src',
+  outExtension: ({ format }) => ({ js: format === 'cjs' ? '.cjs' : '.js' }),
   sourcemap: true,
   treeshake: true,
 };