Adding Terragrunt HCL formatting command

[nayyara-cropsey]

Currently fmt only formats Terraform files but not Terragrunt files.
This adds a command that wraps terragrunt hclfmt allows user to format Terragrunt files with *.hcl extension.

Note this will do nothing if tf_binary == terraform as Terraform cannot be used to format Terragrunt files

[flemux]

It looks like activity on this repo has been stale for a few months, is it no longer maintained?
Could we help out?

[boldandbusted]

I'd love to not see this project die. If there's stuff we can do to help, please let us know. Perhaps some "Good First Issues"? :)