diigital_electricity: Creating gates w/ NAND gate
Levels 13 - 15 focus on creating basic and universal gates using NAND
gate.
- Level 13: Creating AND gate using NAND gate
- Level 14: Creating OR gate using NAND gate
- Level 15: Creating NOR gate using NAND gate
Signed-off-by: Rudra Nil Basu <rudra.nil.basu.1996@gmail.com>