Verify Letter Button

**Wait for https://github.com/deployed/santa-workshop-2022/issues/8 to be completed before proceeding with this task.**
Create a component displaying a 'Verify letter' button and display it in the letters table.
![image](https://user-images.githubusercontent.com/24768155/208115809-ac475b68-e18c-4d92-870e-ac7e80ec27df.png)

Related task: https://github.com/deployed/santa-workshop-2022/issues/24
