Update repositories.txt (arduino#839)

Author: GyverLibs

repositories.txt

@@ -17,6 +17,7 @@ https://github.com/bolderflight/leb128
 https://github.com/bolderflight/framing
 https://github.com/bolderflight/checksum
 https://github.com/bolderflight/airdata
+https://github.com/GyverLibs/SimplePortal
 https://github.com/GyverLibs/GyverHTU21D
 https://github.com/GyverLibs/GyverHC595
 https://github.com/GyverLibs/OVS