output role_arn is incompatible with aws_iam_role_policy_attachment resource

[AlexanderStout]

Issue

aws_iam_role_policy_attachment requires role name, not arn.
in order to attach a policy to the created role "github", either arn string manipulation is needed or hard-coding "github"

Example

`
module "oidc_github" {
source = "unfunco/oidc-github/aws"
version = "1.5.2"

github_repositories = ["org/repo"]
}

resource "aws_iam_role_policy_attachment" "github_role_ecr_policy_attachement" {
role = "github"
policy_arn = aws_iam_policy.ecr_push_policy.arn
}`

Proposed solution:

add role_name output which will consist only of role name