Update creating-an-internal-package.mdx (#8669)

Incorrect use of comma in package.json file

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docs/repo-docs/crafting-your-repository/creating-an-internal-package.mdx

@@ -57,11 +57,11 @@ Next, create the `package.json` for the package. By adding this file, you'll ful
   "exports": {
     "./add": {
       "types": "./src/add.ts",
-      "default": "./dist/add.js",
+      "default": "./dist/add.js"
     },
     "./subtract": {
       "types": "./src/subtract.ts",
-      "default": "./dist/subtract.js",
+      "default": "./dist/subtract.js"
     },
   },
   "devDependencies": {