(draft): Refactor project to be module-based

[jcxldn]

Marked as breaking as every other PR will require changes if this is merged

TODO

• Check publishing and make sure it works to GitHub Packages (use a different repo for this)
• Check publish tasks depends (see below)

// We *probably* don't need this anymore.
tasks.publish.dependsOn build, shadowJar, sources

• Think about how to go about modules in future (eg. stuff like LuckPerms or maybe splitting API up into bungee, bukkit, and common modules?)

[ZachyFoxx]

Closed by #58