Add Linkage to CommonCore and implement SpigotLinker used in BauSystem

CommonCore/Linkage/build.gradle.kts

@@ -0,0 +1,26 @@
+/*
+ *   This file is a part of the SteamWar software.
+ *
+ *   Copyright (C) 2024  SteamWar.de-Serverteam
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU Affero General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU Affero General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Affero General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+plugins {
+    steamwar.java
+}
+
+dependencies {
+    compileOnly(libs.classindex)
+}