feat(build): establish plugin foundation

src/main/java/games/dmg/spigotinventoryhelper/SpigotInventoryHelperPlugin.java

@@ -0,0 +1,10 @@
+package games.dmg.spigotinventoryhelper;
+
+import org.bukkit.plugin.java.JavaPlugin;
+
+public final class SpigotInventoryHelperPlugin extends JavaPlugin {
+    @Override
+    public void onEnable() {
+        getLogger().info("Spigot Inventory Helper enabled.");
+    }
+}

src/main/resources/plugin.yml

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+name: SpigotInventoryHelper
+version: ${version}
+main: games.dmg.spigotinventoryhelper.SpigotInventoryHelperPlugin
+api-version: "1.20"
+description: Inventory sorting and automatic tool replacement utilities.
+author: dmg.games

src/test/java/games/dmg/spigotinventoryhelper/PluginFoundationTest.java

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+package games.dmg.spigotinventoryhelper;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import java.io.InputStream;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+import org.yaml.snakeyaml.Yaml;
+
+final class PluginFoundationTest {
+    @Test
+    void declaresPluginMetadataAndLoadableEntrypoint() throws ClassNotFoundException {
+        InputStream stream = getClass().getClassLoader().getResourceAsStream("plugin.yml");
+        assertNotNull(stream);
+
+        Map<?, ?> plugin = new Yaml().load(stream);
+        assertEquals("SpigotInventoryHelper", plugin.get("name"));
+        assertEquals(
+            "games.dmg.spigotinventoryhelper.SpigotInventoryHelperPlugin",
+            plugin.get("main")
+        );
+        assertEquals("1.20", plugin.get("api-version"));
+        assertNotNull(Class.forName((String) plugin.get("main")));
+    }
+}