Add Adafruit_PCM51xx repository link

[ladyada]

https://github.com/adafruit/Adafruit_PCM51xx

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/adafruit/Adafruit_PCM51xx:

Linting library in Adafruit_PCM51xx
WARNING: library.properties name Adafruit PCM51xx 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, 1 WARNINGS

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Linting sketch in Adafruit_PCM51xx/examples/gpio5_toggle

Linter results for project: no errors or warnings

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Linting sketch in Adafruit_PCM51xx/examples/gpio_test

Linter results for project: no errors or warnings

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Linting sketch in Adafruit_PCM51xx/examples/mclk_test

Linter results for project: no errors or warnings

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Linting sketch in Adafruit_PCM51xx/examples/simpletest

Linter results for project: no errors or warnings

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Linting sketch in Adafruit_PCM51xx/examples/test_PCM51xx

Linter results for project: no errors or warnings

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Linting sketch in Adafruit_PCM51xx/examples/vcom_test

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/adafruit/Adafruit_PCM51xx/