feat: add official Node.js and Python SDKs

- Node.js SDK (sdk/nodejs/): TypeScript, zero deps, native fetch, Node 18+
- Python SDK (sdk/python/): sync + async clients via httpx, Python 3.8+
- Both wrap all conversion endpoints (html, markdown, url, templates)
- Proper error handling with DocFastError
- Full README documentation for each

sdk/nodejs/tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "Node16",
+    "moduleResolution": "Node16",
+    "lib": ["ES2022"],
+    "outDir": "dist",
+    "rootDir": "src",
+    "declaration": true,
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true
+  },
+  "include": ["src"]
+}