Add enrichment lesson A, with media files tracked in LFS

Author: audiodude

enrichment/A_file-system-operations/README.md

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+This directory contains music files sourced from the [Free Music Archive](https://freemusicarchive.org/), licensed under a [Creative Commons BY-NC-ND license](https://creativecommons.org/licenses/by-nc-nd/4.0/).
+
+The artists are:
+
+* [Beech Creeps](https://freemusicarchive.org/music/Beech_Creeps/)
+* [Violet](https://freemusicarchive.org/music/Violet/Let_the_Sunshine_In)
+* [Apache Tomcat](https://freemusicarchive.org/music/Apache_Tomcat/)
+* [The Bowmans](https://freemusicarchive.org/music/The_Bowmans)
+* [The Money Shot](https://freemusicarchive.org/music/The_Money_Shot/)