Setup project correctly for development and release

tsconfig.json

@@ -9,9 +9,10 @@
     "esModuleInterop": true,
     "skipLibCheck": true,
     "forceConsistentCasingInFileNames": true,
+    "strictNullChecks": true,
 
     /* ---- output dir ---- */
     "outDir": "dist"
   },
-  "include": ["src/**/*"]
+  "include": ["src/**/*", "tsdown.config.ts", "eslint.config.ts", "knip.config.ts", "bump.config.ts"]
 }