Update vtx-firmware-update.md

Author: czhou1972

docs/vtx-firmware-update.md

@@ -7,6 +7,7 @@ For Windows system:
 1. Download the HDZeroProgrammer.zip from [HDZero Download](https://www.hd-zero.com/document).    
 2. Extract HDZeroProgrammer.exe from the zip achieve to C:\HDZero
 
+
 For Mac system:
 Great thanks to Gunther Votteler for developing the Mac utility to for the HDZero Programmer. Follow the directions here:
 https://github.com/gvotteler/hdzero-programmer-tool-mac