Add support for terragrunt repo structure

[leggomuhgreggo]

Hello!

• Vote on this issue by adding a 👍 reaction
• If you want to implement this feature, comment to let us know (we'll work with you on design, scheduling, etc.)

Issue details

Wanted to try the conversion tool on an existing terraform project that uses terragrunt. When I run

 pulumi convert --from terraform --language typescript --out pulumi

I get boilerplate Pulumi.yaml and index.ts files

// Pulumi.yaml
name: terraform-infrastructure
runtime: nodejs

// index.ts
import * as pulumi from "@pulumi/pulumi";

Thanks for your consideration!