Update repositories.txt (#2407)

Naguissa · web-flow · commit fb74e19228b4 · 2023-01-23T10:16:54.000Z
Add Naguissa/uUnixDate library - Tiny and simplified library to convert to and from UNIX timestamps.
diff --git a/repositories.txt b/repositories.txt
@@ -5535,3 +5535,4 @@ https://github.com/TrebledJ/Serial-Tuning
 https://github.com/arduino-libraries/Arduino_ESP32_OTA
 https://github.com/stoneroweast/HoldButton
 https://github.com/jpconstantineau/BlueMicro_RP2040_Arduino_Library.git
+https://github.com/Naguissa/uUnixDate
