Dependency ecosystems not correctly detected

[martincostello]

The logic to detect whether to configure package updates for most ecosystems, except for GitHub Actions and Terraform only appears to consider files in the root of the repository.

I found this after testing the action out on a .NET repository where the .csproj files are in subdirectories within the repository. The action generated a dependabot.yml file that only specified GitHub Actions updates.

Each file tested for should recurse through the repository to try and files (maybe within a configurable depth limit to reduce impact on rate limits) so that the generated file is a more accurate reflection of what should be configured.