[02dec21] Minor Update

Very minor update this time.

• Section 2.1: Renamed a few of the tougher Attempt Difficulties, to make them more distinct from the Adventurer Tiers.
• Section 3.1: 
  • Renamed three Adventurer Tiers. Cosmetic change only.
    
  • Added two new Adventurer Tiers. Now there are an even 10 Tiers.