Add DEVFULL

[RobTillaart]

DEVFULL mimics the /dev/full device of Linux, can be used for testing.

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/RobTillaart/DEVFULL:

Linting library in DEVFULL
WARNING: A commonly misspelled word was found in the library.properties paragraph field. Suggested correction: useful   
         for testing with streams (Rule LP035)                                                                          

Linter results for project: 0 ERRORS, 1 WARNINGS

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Linting sketch in DEVFULL/examples/DEVFULL_demo

Linter results for project: no errors or warnings

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Linting sketch in DEVFULL/examples/DEVFULL_performance

Linter results for project: no errors or warnings

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Linter results for projects: 0 ERRORS, 1 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/RobTillaart/DEVFULL/