Add Js5Archive object

This will eventually hold the names of each JS5 archive in 550, as and
when I confirm the names from the NXT beta client still match up with
the functionality of each archive in 550.

Currently it only holds then name of index 255.

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

cache/src/main/java/dev/openrs2/cache/Js5Archive.kt

@@ -0,0 +1,5 @@
+package dev.openrs2.cache
+
+public object Js5Archive {
+    public const val ARCHIVESET: Int = 255
+}