feat: add minimal Task scheduler

[belem2050]

Minimal Task scheduler for beginners.

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/belem2050/TaskScheduler:

Linting library in TaskScheduler
INFO: No header file found matching library name (LightTaskScheduler.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: No license file found.                                                                                                                 
         See:                                                                                                                                   
         https://docs.github.com/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository
         (Rule LD002)                                                                                                                           
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, 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/belem2050/TaskScheduler/