Terragrunt is a thin wrapper for terraform, you can read more about it here:
This extension installs terragrunt AzureDevops build agents, can be used in both build and release pipelines. There is currently no corresponding command task, all terragrunt commands will have to be run from a generic bash, cmd or powershell task.
Make sure node and typescript are installed, navigate to installTerragrunt & run
npm install
tsc
mocha tests/_suite.js
This task was created by following this article, if your having trouble getting started try following the setup steps before posting an issue.