Add missed license header

Author: Jonathing

src/main/java/net/minecraftforge/gitver/api/package-info.java

@@ -1,3 +1,7 @@
+/*
+ * Copyright (c) Forge Development LLC
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
 @NotNullByDefault
 package net.minecraftforge.gitver.api;