[RA-1191] Create step

[tothszabi]

Checklist

• I've read and followed the Contribution Guidelines
• step.yml and README.md is updated with the changes (if needed)

Version

Requires a MAJOR version update

Context

This is the first version of the step. It is very simple and at the moment does not do much. It just calls an endpoint with the user provided values which will schedule a new release in the Bitrise release management. It also exports some values from the response so the users can use them in their workflow.

The only endpoint this step uses is this one:
https://api-docs.bitrise.io/#/releases/release-create-app-store

Changes

• The step follows the ideal step architecture
• The networking is implemented in the client.go file
• The step does not have any e2e test at the moment because I do not see any way I could a meaningful one
• The step will have two outputs but at the moment only one of them implemented in the backend so the other value is commented out and left in the PR as a placeholder