added health display for the game and gave the player the ability to use potion to heal themselves

We added a health bar for the player and each enemy entity in the game.  This makes the game more playable because players now know what their current hp is.

We created a new potion class and made it a component of the player entity.  Players can now press 1 to consume a potion and heal themselves.  Each game Player start out with 5 potion.  This makes the game lasts longer and gives the player more freedom to explore the dungeon