Project: mobx
Task (easy): 1) Create a BlogForm component as a appealing Modal with the title 'Create Blog'. 
2) Use MobX to manage the 'formVisible' state. When formVisible is true, the BlogForm should be displayed, otherwise, it should be hidden.
3) Add an 'Add Blog' appealing blue button in the right of Header.tsx to toggle the BlogForm's visibility. 
4) Place a close button (.close-btn) with 'x' in the top right of BlogForm to hide it.
5) Place the BlogForm component in App.tsx. Use observer in mobx-react-lite to auto update.