chore: exclude test files from the build output

tsconfig.json

@@ -1,6 +1,7 @@
 {
   "extends": "@sindresorhus/tsconfig",
+  "exclude": ["src/**/*.test.ts"],
   "compilerOptions": {
-    "outDir": "./lib",
+    "outDir": "./lib"
   }
-}
+}