[Enhancement] Now allow for custom implementations of EventWaiter

[Shengaero]

Pull Request

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Pull Request Information

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• [ ] My PR fixes a bug, error, or other issue with the library's codebase.
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Description

Due to the recent EventWaiter requests (among them, asynchronous dispatch of EventListener#onEvent, concurrent-modification support, and others I am probably missing), there will now be a new interface as part of the commons module: IEventWaiter

This will allow for developers to have even the tiniest specifications they might desire at their disposal when dealing with the menus in the menu module, and other general specifics.

An example implementation in kotlin can be found here.

Please note that if you currently use EventWaiter this PR is 100% backwards compatible, and you should have no codebase changes required upon the release of next version.

[Shengaero]

This newest commit should also address #60 For anyone who still encounters issues, you should consider implementing IEventWaiter

[schnapster]

Any help needed to move this PR along? Suffering from #60

[Shengaero]

@napstr if you absolutely need this PR right now, you can check it out via jitpack.

[Andre601]

Just wanted to point out that the linked Gist is invalid (doesn't exist)