Add HC4051 library for 1x8 multiplexer (#2417)

Author: RobTillaart

repositories.txt

@@ -3552,6 +3552,7 @@ https://github.com/RobTillaart/FunctionGenerator
 https://github.com/RobTillaart/GAMMA
 https://github.com/RobTillaart/GST
 https://github.com/RobTillaart/GY521
+https://github.com/RobTillaart/HC4051
 https://github.com/RobTillaart/HC4067
 https://github.com/RobTillaart/HeartBeat
 https://github.com/RobTillaart/Histogram