Update repositories.txt

[cparata]

Please, add STM32duino MotionFX library to the Library Manager.
Thanks in advance.
Carlo

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/stm32duino/MotionFX:

Linting library in MotionFX
INFO: No header file found matching library name (STM32duino_MotionFX.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 STM32duino MotionFX 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.properties name STM32duino MotionFX contains spaces. Although supported, best practices is to not use  
         spaces.                                                                                                        
         See: https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format         
         (Rule LP015)                                                                                                   

Linter results for project: 0 ERRORS, 2 WARNINGS

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

Linting sketch in MotionFX/examples/Fusion6X_IKS01A2

Linter results for project: no errors or warnings

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Linting sketch in MotionFX/examples/Fusion6X_IKS01A3

Linter results for project: no errors or warnings

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

Linting sketch in MotionFX/examples/Fusion6X_IKS02A1

Linter results for project: no errors or warnings

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

Linting sketch in MotionFX/examples/Fusion9X_IKS01A2

Linter results for project: no errors or warnings

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

Linting sketch in MotionFX/examples/Fusion9X_IKS01A3

Linter results for project: no errors or warnings

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

Linting sketch in MotionFX/examples/Fusion9X_IKS02A1

Linter results for project: no errors or warnings

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

Linter results for projects: 0 ERRORS, 2 WARNINGS

[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/stm32duino/MotionFX/