Add search icon in search bar

## Is your enhancement request related to a problem? Please describe

![image](https://github.com/apache/incubator-answer/assets/360618/ee84d4f3-4b63-43ab-9f4d-3df528e10efb)

The search button allows for a more intuitive presentation

## Describe the solution you'd like

![image](https://github.com/apache/incubator-answer/assets/360618/a4f22358-4d9c-4273-b1be-5561d970fe52)


