Add compatibility with jitpack.io

[ks-hl]

This PR allows NexEngine to be used as a Maven dependency through jitpack.io

i.e

    <dependency>
        <groupId>com.github.nulli0n</groupId>
        <artifactId>NexEngine-spigot</artifactId>
        <version>v2.2.11</version>
    </dependency>```

Edit: The intention is to make ExcellentCrates also usable through Jitpack, but this dependency must be accessible through Maven first.

[nulli0n]

How does this works?

[ks-hl]

How does this works?

It basically just fixes an issue with encoding and also the jitpack.yml gives instructions for the jitpack compiler so it forces it to use Java 16 vice 8. Does not affect anything with the project itself.