update build script (add buildSrc)

buildSrc/build.gradle.kts

@@ -0,0 +1,11 @@
+plugins {
+    // Support convention plugins written in Kotlin. Convention plugins are build scripts in 'src/main' that automatically become available as plugins in the main build.
+    `kotlin-dsl`
+}
+
+repositories {
+    // Use the plugin portal to apply community plugins in convention plugins.
+    gradlePluginPortal()
+}
+dependencies {
+}

buildSrc/src/main/kotlin/net.nuggetmc.java-conventions.gradle.kts

@@ -0,0 +1,6 @@
+plugins {
+    `java-library`
+}
+
+group = "net.nuggetmc"
+version = "3.3.1-BETA"