- Proper level storage and generate next level after first one has been loaded

[todo]

https://github.com/oref/SiliconBlood/blob/7396e75b9c3744242dd8fd94081c2dcbb5ff429e/ecs/level/level.py#L3-L6

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This issue was generated by todo based on a TODO comment in 7396e75. It's been assigned to @Oref because they committed the code.