Update repositories.txt to include 3 new Libraries (#4088)

Adding 3 new Libraries made by Author: Brayden Anderson (@braydenanderson2014)

Author: braydenanderson2014

repositories.txt

@@ -6695,4 +6695,7 @@ https://github.com/braydenanderson2014/ArduinoLinkedList
 https://github.com/braydenanderson2014/SimpleVector
 https://github.com/braydenanderson2014/ArduinoSDList
 https://github.com/braydenanderson2014/ArduinoHashtable
+https://github.com/braydenanderson2014/ArduinoTimer
+https://github.com/braydenanderson2014/SimpleProperties
+https://github.com/braydenanderson2014/UnorderedMap
 https://github.com/qqqlab/madflight