Update repositories.txt (#5835)

Author: dejwk

repositories.txt

@@ -1867,6 +1867,7 @@ https://github.com/DefProc/lewis
 https://github.com/DefProc/somo-ii-lib
 https://github.com/DeimosHall/RP2040_CPU_Temperature.git
 https://github.com/DEIS-Tools/CLAIRE-library
+https://github.com/dejwk/roo_backport
 https://github.com/dejwk/roo_collections
 https://github.com/dejwk/roo_control
 https://github.com/dejwk/roo_display