Update #0002.3

Update #0002.3 released. Add 2 intros and 4 new challenges.

• Intro to parallel computing.
• Intro to calculator.
• 1 new challenge on Exclusive Or. Easy difficulty.
• 1 new challenge on Expansion. Easy difficulty.
• 1 new challenge on Permutation. Easy difficulty.
• 1 new challenge on Expansion Permutation. Easy difficulty.