Create root directory in tar/zip files

Signed-off-by: Graham <gpe@openrs2.org>

cache/src/main/kotlin/org/openrs2/cache/DiskStoreZipWriter.kt

@@ -42,6 +42,9 @@ public class DiskStoreZipWriter(
 
     init {
         out.setLevel(level)
+
+        out.putNextEntry(createZipEntry(""))
+
         out.putNextEntry(createZipEntry("main_file_cache.dat2"))
         out.write(zeroBlock)
     }

cache/src/main/kotlin/org/openrs2/cache/FlatFileStoreTarWriter.kt

@@ -24,6 +24,11 @@ public class FlatFileStoreTarWriter(
 ) : Store {
     private val timestamp = Date.from(timestamp)
 
+    init {
+        out.putArchiveEntry(createTarEntry("", size = 0))
+        out.closeArchiveEntry()
+    }
+
     private fun createTarEntry(name: String, size: Int): TarArchiveEntry {
         val entry = TarArchiveEntry(prefix + name)
         entry.modTime = timestamp