Add firmware badge

0x007E · 0x007E · commit 3ffe2e6b8cc8 · 2025-09-13T18:44:46.000+02:00
diff --git a/README.md b/README.md
@@ -1,4 +1,4 @@
-[![Version: 1.0 Release](https://img.shields.io/badge/Version-1.0%20Release-green.svg)](https://github.com/0x007e/diu) ![Build](https://github.com/0x007e/diu/actions/workflows/release.yml/badge.svg) [![License CC By-NC-SA](https://img.shields.io/badge/Hardware-CC--BY--NC--SA--4.0-lightgrey)](https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode)
+[![Version: 1.0 Release](https://img.shields.io/badge/Version-1.0%20Release-green.svg)](https://github.com/0x007e/diu) [![License CC By-NC-SA](https://img.shields.io/badge/Hardware-CC--BY--NC--SA--4.0-lightgrey)](https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode) [![License GPLv3](https://img.shields.io/badge/Firmware-GPLv3-lightgrey)](https://www.gnu.org/licenses/gpl-3.0.html) ![Build](https://github.com/0x007e/diu/actions/workflows/release.yml/badge.svg)
 
 # `DIU` - Digital (Analog) Clock (Digitaluhr)
 

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-[![Version: 1.0 Release](https://img.shields.io/badge/Version-1.0%20Release-green.svg)](https://github.com/0x007e/diu) ![Build](https://github.com/0x007e/diu/actions/workflows/release.yml/badge.svg) [![License CC By-NC-SA](https://img.shields.io/badge/Hardware-CC--BY--NC--SA--4.0-lightgrey)](https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode)`
	`1`	`+[![Version: 1.0 Release](https://img.shields.io/badge/Version-1.0%20Release-green.svg)](https://github.com/0x007e/diu) [![License CC By-NC-SA](https://img.shields.io/badge/Hardware-CC--BY--NC--SA--4.0-lightgrey)](https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode) [![License GPLv3](https://img.shields.io/badge/Firmware-GPLv3-lightgrey)](https://www.gnu.org/licenses/gpl-3.0.html) ![Build](https://github.com/0x007e/diu/actions/workflows/release.yml/badge.svg)`
`2`	`2`
`3`	`3`	# `DIU` - Digital (Analog) Clock (Digitaluhr)
`4`	`4`