Redundant naming constraint on examples

### Terraform CLI and terraform-plugin-docs Versions

```
Terraform v1.14.2
on darwin_arm64
```

```
github.com/hashicorp/terraform-plugin-docs v0.24.0 // indirect
```

### Provider Code

```go
N/A
```

### Expected Behavior

I would expect when I put an example in folder that respect the folder naming convention and my file is named `foobar.tf` for instance that it would show up when I generate the documentation.

### Actual Behavior

My file is not picked up and instead i have to name my example `resource-foobar.tf`

### Steps to Reproduce

1. `tfplugindocs generate --flags`

### How much impact is this issue causing?

Low

### Logs

_No response_

### Additional Information

I'm not sure to understand why there is a requirement on the name of the file in the final folder, the rest of the path can be used to infer it is a resource example so I'm not sure to understand why this requirement is in place.

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct