dev: switch to stonecutter build system

- This will allow us to build the library for different Minecraft versions at the same time
- Right now, only Fabric and Neoforge 1.21.10 are fully working
- As a bonus, the jar is now even smaller!

buildSrc/build.gradle.kts

@@ -0,0 +1,8 @@
+plugins {
+    `kotlin-dsl`
+    kotlin("jvm") version "2.0.20"
+}
+
+repositories {
+    mavenCentral()
+}