input: Write a function that creates a Python Flask app to handle POST requests on the '/webhook' route. The function should extract necessary parameters from the request and use the 'makeWebhookResult' function to generate a JSON response containing a 'speech' field. The app should be started on port 5000 and run in debug mode. Here is the function header: "def create_flask_app():".
  
  assert create_flask_app() is not None
  assert makeWebhookResult({"result": {"action": "producto.info", "parameters": {"producto": "hogar"}}})["speech"].startswith("Buscando informacion del producto")
output: def create_flask_app():
      from flask import Flask, request, jsonify
  
      app = Flask(__name__)
  
      @app.route('/webhook', methods=['POST'])
      def webhook():
          req = request.get_json(silent=True, force=True)
          result = req.get("result")
          parameters = result.get("parameters")
          producto = parameters.get("producto")
          response = makeWebhookResult({"result": {"action": "producto.info", "parameters": {"producto": producto}}})
          return jsonify(response)
  
      app.run(port=5000, debug=True)
      return app