Support uppercase letters in inventory item names for the "view inventory" command and skill names for the "view skills" command

[HarrisonD123]

Currently, the "view inventory" and "view inventory [inventory-item]" commands don't support uppercase letters in inventory item names. This is because the CLI team lowercases all strings inputted by the user before passing them to our do_action functions. This causes our display_inventory and display_inventory_item functions in game-state/player.c to be unable to find items with capital letters, given that they are passed lowercased strings. This should be a fairly simple fix that involves ignoring capitalization in the display_inventory and display_inventory_item functions.

The same applies to skills in the display_tree and display_skill_description functions in skilltrees/skilltree.c for the "view skills" and "view skills [skill-name]" commands.