Fix error when loading the same asset bundle from multiple providers

[AmongUsafk]

Related to #7

Implements a shared caching system for AssetBundle instances in EmbeddedAssetBundleProvider to prevent errors when loading the same asset bundle from multiple instances.

• Introduces a static Dictionary<string, AssetBundle> to keep track of loaded AssetBundle instances by their names, ensuring that each bundle is loaded only once across all instances of EmbeddedAssetBundleProvider.
• Modifies the Load method to first check the static dictionary for an existing AssetBundle before attempting to load a new one, effectively using the shared cache.
• Adjusts the CoLoad coroutine method to also check the static dictionary for a cached AssetBundle before loading, and upon successful asynchronous loading, the loaded bundle is added to the shared cache.
• Ensures that when an AssetBundle is loaded, either synchronously or asynchronously, it is added to the static dictionary, preventing duplicate loads and eliminating the error when attempting to load the same asset bundle from different instances.

[AmongUsafk]

@DaemonBeast

[DaemonBeast]

Thank you for your contribution, but there are a few problems with your code and I already have a fix for this issue that I will push soon.