Update repositories.txt

[xiaoming-sun6]

No description provided.

[github-actions]

❌ ERROR: Arduino Lint found errors with https://github.com/xiaoming-sun6/Arduino-SerialDebugger:

Linting library in Arduino-SerialDebugger
INFO: No header file found matching library name (Arduino_SerialDebugger.h). Best practices are for primary header      
      filename to match library name. (Rule LS008)                                                                      
WARNING: library.properties name value Arduino SerialDebugger is longer than the recommended length of 16 characters.   
         (Rule LP010)                                                                                                   
ERROR: Library name Arduino SerialDebugger starts with "Arduino". These names are reserved for official libraries. (Rule
       LP012)                                                                                                           
WARNING: library.properties name Arduino SerialDebugger contains spaces. Although supported, best practices is to not   
         use spaces. (Rule LP015)                                                                                       

Linter results for project: 1 ERRORS, 2 WARNINGS

-------------------

Linting sketch in Arduino-SerialDebugger/examples/baseUse

Linter results for project: no errors or warnings

-------------------

Linter results for projects: 1 ERRORS, 2 WARNINGS

[github-actions]

Thanks for your interest in contributing to the Arduino Library Manager index @xiaoming-sun6
Please resolve the error(s) mentioned in the previous comment.

After resolving the issue, trigger this check again by doing one of the following:

• Commit the required change to the branch you submitted this pull request from.
• Comment here, mentioning @ArduinoBot in the comment.

❗ NOTE: It is not necessary to open a new pull request. ❗

More information:
https://github.com/arduino/library-registry/blob/main/README.md#if-the-problem-is-with-the-pull-request

[per1234]

Successfully submitted via #794