fix: update CITATION.cff version to 0.4.0

Author: larsrollik

CITATION.cff

@@ -2,7 +2,7 @@ cff-version: 1.2.0
 message: "If you use this software, please cite it as below."
 type: software
 title: "ttl-barcoder: TTL barcode generation for multi-system DAQ synchronization"
-version: "0.3.0"
+version: "0.4.0"
 repository-code: https://github.com/murineshiftwork/ttl-barcoder
 license: BSD-3-Clause
 authors: