Update repositories.txt

[mongonta0716]

No description provided.

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/stack-chan/stackchan-arduino:

Linting library in stackchan-arduino
INFO: No header file found matching library name (stackchan-arduino.h). Best practices are for primary header filename  
      to match library name.                                                                                            
      See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format            
      (Rule LS008)                                                                                                      
WARNING: library.properties name value stackchan-arduino is longer than the recommended length of 16 characters.
         See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format 
         (Rule LP010)                                                                                           
WARNING: Library name stackchan-arduino contains "Arduino". This is superfluous.                               
         See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format
         (Rule LP014)                                                                                          
WARNING: No example sketches found. Please provide examples.                                      
         See: https://arduino.github.io/arduino-cli/latest/library-specification/#library-examples
         (Rule LD004)                                                                             

Linter results for project: 0 ERRORS, 3 WARNINGS

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[github-actions]

Your submission has now been accepted! Thanks for your contribution to the Arduino Library Manager index.

The library(s) will be available for installation via Library Manager within a day's time.

You can check the logs from the Library Manager indexer for your library(s) here:
http://downloads.arduino.cc/libraries/logs/github.com/stack-chan/stackchan-arduino/