Update README.md

Author: TheKitty

README.md

@@ -46,7 +46,7 @@ Adafruit_Learning_System_Guides, not a sub-directory):
 ```
 ## Licensing
 
-Adafruit Learning System code files should have author and license information conforming to the open SPDX specification.
+Adafruit Learning System code files should have author and license information conforming to the open [SPDX specification](https://www.iso.org/standard/81870.html).
 See [this page](https://learn.adafruit.com/contribute-to-the-adafruit-learning-system-with-git-and-github/add-author-and-license-information) for more.
 
-Updated November 27, 2023
+Updated November 29, 2023