add scenarios and parameters sections

<!-- Identify clearly the benefits will help the community to contribute on your job -->

## Use cases

<!-- Explain how the job could work -->

### Scenarios

<!-- Using the Gherkin syntax (see https://cucumber.io/docs/gherkin/reference/)

describe several scenarios of the job working. Example for Gitlab release

creation job:

Scenario: With a `CHANGELOG.md` file

* Given there is a `CHANGELOG.md` file in repository

* When the job is run on a pipeline on default branch

* Then a new Gitlab release is created using:

    * `name`, `description`, `milestones`, `assets:links` from `CHANGELOG.md`

    * `tag_name` from `name`

    * `ref` from `$CI_COMMIT_SHA`

-->

### Parameters

<!-- Describe here the parameters of the job. Example for Gitlab release

creation job:

| Name | Mandatory to create release ? | Default | How to get it ? |

| ---- | ----------------------------- | ------- | --------------- |

| `name` | yes | if `CHANGELOG.md` exists: from this file. Else, use the current date and commit SHA | Parse `CHANGELOG.md`. Else, use `YYYY-MM-DD.$CI_COMMIT_SHORT_SHA` |

| `tag_name` | yes | same as `name` | get value set to `name` |

| `ref` | yes | current commit | use Gitlab variable `$CI_COMMIT_SHA` |

| `description` | no | get it from `CHANGELOG.md` if it exists | parse `CHANGELOG.md` |

| `milestones` | no | get it from `CHANGELOG.md` if it exists | parse `CHANGELOG.md` |

| `assets:links` | no | get it from `CHANGELOG.md` if it exists | parse `CHANGELOG.md` |

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## Artifacts & Return status

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