Lightweight Web Chatbot App

I’m looking for a concise, browser-based chatbot that users can open in any modern web browser, type a question, and immediately receive a natural-language reply. At this stage I’m focused only on the web version—no mobile builds are necessary... (Budget: $250 - $750 USD, Jobs: API Development, Chatbot, HTML, JavaScript, Natural Language Processing, Node.js, PHP, Python)