Add an inventory system to the game

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I'm just making this so we can track the progress of the system's development.

Linting status:

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Progress Update

I have redone the inventory system to have a less complicated design which should make development of new items easier.

The next things I plan to work on are:

1. Add the ability to remove items from an inventory
2. Add the ability to serialize/deserialize both an entire inventory and individual items.

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Progress Update:

Note: :heavy_check_mark: -> In progress :white_check_mark: -> Done :x: -> Not started

While I want to finish off the inventory system, I think getting a functional UI for the system is also important so I am going to (most likely) devote all of today working on things that are not directly related to the inventory system. The things I plan on working on include:

• :white_check_mark: Add a tool-tip when the user hovers over an item, displaying more information about the item. This may require a few tweaks to the inventory system, but they should be minor.
• :white_check_mark: Sprucing up the individual item slots to fit the theme of the game a bit better.
• :white_check_mark: Add some more enemies to the boss level for the first floor to make it harder.

Once I get back to working on the actual system, I will probably work on these things:

• :white_check_mark: Add a better method for query information about a particular inventory item.
• :heavy_check_mark: Add a very rudimentary chest to see how the current design of the inventory system can be applied to non-player inventories. I probably will change the system to make it more of a generally applicable system.
• :x: Add a way to transfer items to another inventory instance.
• :x: Add a better method for removing items from the inventory.
• :white_check_mark: Add methods to serialize and deserialize an instance.

This will most certainly span many days, but I plan to get them all done. I'll update the post as I go.