Add status badges

Author: aliphys

README.md

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 # Arduino_POSIXStorage Library
 
+[![Check Arduino](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/check-arduino.yml/badge.svg)](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/check-arduino.yml) [![Compile Examples](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/compile-examples.yml/badge.svg)](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/compile-examples.yml) [![Spell Check](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/spell-check.yml/badge.svg)](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/spell-check.yml) [![Sync Labels](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/sync-labels.yml/badge.svg)](https://github.com/arduino-libraries/Arduino_POSIXStorage/actions/workflows/sync-labels.yml)
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 The Arduino_POSIXStorage Library complements the POSIX storage functions already included in the Renesas core and the Arduino_USBHostMbed5 library, and makes them available to sketches.
 
 For more information about this library please read the documentation [here](./docs/).