Add 'addCheck' method to CommandManager

In my opinion, the main problem with command frameworks is that you never have full control over them, which can result in either having to do some hacky methods to get it to do what you want, or just not using the framework but your own solution.

Issue #57 is a good example of this. If you want to add a default cooldown/per command cooldown, you’ll have to modify ACF for it to work. My idea is to add a method to the CommandManager, something along the lines of CommandManager#addCheck(Check), where Check is a functional interface which looks like this:

interface Check {
    boolean check(Sender sender, String name, String[] args, Method method);
}

Again, using Issue #57 as an example, you can do this:

myCommandManager.addCheck((sender, name, args, method) -> {
    boolean hasCooldown; //check if sender has cooldown
    if(hasCooldown) return false; //Command will not be executed
    
    int cooldown = method.getAnnotation(CommandCooldown.class).value(); //get cooldown (or default cooldown)
    //set cooldown for sender
   return true; //Command will be executed
});

[aikar]

I’m trying to move away from Override style stuff. Precommand is close, but I am working on something for this, but the name will be Preconditions

[chickeneer]

https://github.com/aikar/commands/blob/f900a739df7bfc0c1b6779be196541937209ddaf/core/src/main/java/co/aikar/commands/BaseCommand.java#L415

In the current version of ACF, one can override this method from BaseCommand to accomplish some of these ideas. The method is called here: https://github.com/aikar/commands/blob/8168122241d56fc6278ef4ab2197b0ef5ddd1dc0/core/src/main/java/co/aikar/commands/RegisteredCommand.java#L133

(Just giving the context for how this would fit into existing code).