input: Write a function to create a Python Flask app that listens for POST requests on the '/webhook' route. When a request is received, it should extract the necessary parameters from the request and call the 'makeWebhookResult' function to generate a response. The response should be a JSON object containing a 'speech' field with the text to be spoken by the voice assistant. The app should be started on port 5000 and run in debug mode.
  
  assert create_flask_app() == (True, \<app-instance\>)
  assert create_flask_app() == (False, "Error in creating the Flask app")
output: def create_flask_app():
      try:
          from flask import Flask, request, jsonify
          app = Flask(__name__)
  
          @app.route('/webhook', methods=['POST'])
          def webhook():
              req = request.get_json(silent=True, force=True)
              res = makeWebhookResult(req)
              return jsonify(res)
  
          app.run(port=5000, debug=True)
          return (True, app)
      except Exception as e:
          return (False, "Error in creating the Flask app")