message: Added Discord Server
diff: [Competitive Programmer's Handbook](https://cses.fi/book/book.pdf) An important book to improve competitive programming skills.
  +### Awesome Discord Server Community
  +
  +[Priyansh31dec Server](https://discord.gg/MzTxQDCP)
  +
  +[Errichto Server Official](https://discord.gg/mavn2aeb)
  