fix(docs): add Wayback Machine archive URL for PyTorch Lightning mask detection tutorial

Author: ferkans-amir

README.md

@@ -504,7 +504,7 @@ To get started, simply fork this repo. Please refer to [CONTRIBUTING.md](CONTRIB
 - [Code a Smile Classifier using CNNS in Python](https://github.com/kylemcdonald/SmileCNN)
 - [Natural Language Processing using scikit-learn](https://towardsdatascience.com/natural-language-processing-count-vectorization-with-scikit-learn-e7804269bb5e)
 - [Code a Taylor Swift Lyrics Generator](https://towardsdatascience.com/ai-generates-taylor-swifts-song-lyrics-6fd92a03ef7e)
-- [Mask detection using PyTorch Lightning](https://towardsdatascience.com/how-i-built-a-face-mask-detector-for-covid-19-using-pytorch-lightning-67eb3752fd61)
+- [Mask detection using PyTorch Lightning](https://web.archive.org/web/20201101020214/https://towardsdatascience.com/how-i-built-a-face-mask-detector-for-covid-19-using-pytorch-lightning-67eb3752fd61)
 
 ### Miscellaneous: