input: Write a function named `run_flask_app` to start a Flask app that listens for POST requests on the '/webhook' route. When a request is received, 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 run_flask_app(port=5000, debug=True)
output: 
  def run_flask_app(port, debug):
      from flask import Flask, request, jsonify
  
      app = Flask(__name__)
  
      @app.route('/webhook', methods=['POST'])
      def webhook():
          req = request.get_json(silent=True, force=True)
          response = makeWebhookResult(req)
          return jsonify(response)
  
      app.run(port=port, debug=debug)
  