Add combat stats to Character class

[eric-blue]

The Character class (used by both player and NPCs) should be extended to allow for tracking combat stats

• [x] add character-stats.ts module alongside character.ts
• [x] stats module should be imported in 1.ts into both the player and all enemy NPCs
• [x] expand the stats object reference in Character to store the new stats, along with new defaults
  • health, damage, ac, whatever else we may need?
• [x] create method(s) for setting the health stat to new values
  • damage(123) and heal(123)
• [x] player only: everytime the above method(s) is called, save the stats to the gamestate alongside playerPosition. Load these stats into the player Character when the game starts (hint: search for playerPosition in 1.ts)