Allow passing multiple existing bucket names

[berkguzel]

I want to scan multiple existing S3 buckets but it looks like I have to create new lambda function for each S3 bucket.

I think it would be better to have an existing buckets name array to pass multiple S3 bucket name.

In current scenerio, I have to apply terraform code for each existing S3 bucket.

[carlosmmatos]

@berkguzel Thanks for opening up the issue. We will be taking a look into this for you to see what we can do to allow passing in multiple buckets.