refactor: ♻️ unique ids optional_dependencies - dependencies (#308)

Added validation to check for the same mod_ids in `optional_dependencies` and `dependencies`

Technically, it may break mods that have the same `mod_id` listed in both the `optional_dependencies` and `dependencies` sections. However, since the `optional_dependencies` feature was introduced in v6.0.0, it is highly unlikely that such conflicts exist.

Author: KANAjetzt

addons/mod_loader/resources/mod_manifest.gd

@@ -110,6 +110,12 @@ func _init(manifest: Dictionary) -> void:
 			incompatibilities,
 			["dependencies", "incompatibilities"]
 		) or
+		not validate_distinct_mod_ids_in_arrays(
+			mod_id,
+			optional_dependencies,
+			dependencies,
+			["optional_dependencies", "dependencies"]
+		) or
 		not validate_distinct_mod_ids_in_arrays(
 			mod_id,
 			optional_dependencies,