THIS IS A DATAPACK! You need to either add it to your world's datapack folder or use an automatic loader such as OpenLoader or Paxi.
This datapack fixes a bug present in Iron Chests Restocked for over 2 years that makes barrels not mineable, making them not drop unless you explode them and take ages to mine.
Thanks to koshell on GitHub for giving this into my attention in the Prominence issue tracker.
How to install?
Download the zip and put it in your world's datapacks folder.
Alternatively, install openloader or paxi, and put the datapack inside their data folder.