[Enhancement] Replace the default directories with FHS and XDG-adherent ones.

[RokeJulianLockhart]

Is your feature request related to a problem?

The defaults pollute $HOME/Documents:

$HOME/Documents
├── EpicVault
├── Unreal Engine
└── Unreal Projects

...also, with inconsistent names:

Describe the solution you'd like

They should ideally be outside ./Documents (inside $HOME/.local/share, per FreeDesktop and the FHS), and all inside a superordinate "EpicAssetManager" directory, like:

$HOME/.local/share/EpicAssetManager
├── EpicVault
├── UnrealEngine
└── UnrealProjects

Describe alternatives you've considered

Group them inside an "EpicAssetManager" directory inside $HOME (or ./Documents):

$HOME/EpicAssetManager
├── EpicVault
├── UnrealEngine
└── UnrealProjects

This wouldn't adhere the aforementioned standards.

Additional context

Regardless:

┌── EpicVault
├── Unreal Engine
└── Unreal Projects

...should become:

┌── EpicVault
├── UnrealEngine
└── UnrealProjects

...or, slightly worse yet:

┌── Epic Vault
├── Unreal Engine
└── Unreal Projects