Let users add custom columns beyond the 4 defaults👤

[anoopcodehack]

File: client/src/components/Board/KanbanBoard.jsx
Board is hardcoded to 4 columns only.
Add an "+ Add Column" button at the end.
Store custom columns in localStorage for now.
~20 lines!

[Jiyavur14]

Hii, i would like to work on this issue, could you assign it to me?