docs: update the README with the new behavior

## Description

**R2Devops hub** is a collaborative hub of CI & CD **ready to use** jobs which

**R2Devops hub** is a collaborative hub of CI & CD **ready to use** templates which

helps you to quickly build powerful pipelines for your projects.

This mono-repo contains several parts:

* Jobs' sources and a job template (jobs structure is described in [documentation](https://docs.r2devops.io/public-catalog/contribute/#template-definition))

* templates' sources (structure is described in [documentation](https://docs.r2devops.io/public-catalog/contribute/#template-definition))

* Documentation of the hub

* Tools used in hub pipeline to check jobs

* Tools used in hub pipeline to check templates

* Template R2 files, that defines template metadata

```

.

├── docs            # Documentation sources

├── jobs            # Folder containing jobs sources

├── jobs            # Folder containing templates sources

│   └── ...

├── mkdocs.yml      # Documentation configuration

├── Pipfile         # Pipenv dependency file to build doc

    └── ...

```

### How to add or update a job

### How to add or update a template

* Follow the [Contributing guide](https://docs.r2devops.io/public-catalog/contribute)

1. `ci_linter`  

This jobs use the [CI lint API](https://docs.gitlab.com/ee/api/lint.html) to validate the configuration of each jobs.yaml file. 

2. `job_structure`  

This job written in Python ensures every files respect the structure we want. It checks that every file has the right name, the right path and the right content. 

1. `job_image_scan`  

Runs only on merge request.

This job uses [trivy](https://aquasecurity.github.io/trivy/) to scan images listed in template files that have been modified. It checks that the image doesn't have any vulnerability.

3. `job_customs`  

This job written in Python ensures every script of the jobs doesn't made modifications on the repository. It checks that every script doesn't use `git commit` or `git push`.

4. `job_image_scan`  

Runs only on the default branch. And uses some cache for the images.

This job uses [trivy](https://aquasecurity.github.io/trivy/) to scan all images used in the jobs. It checks that the image doesn't have any vulnerability.

5. `code_spell`

1. `code_spell`

This job uses codespell to check the spelling of the code. It checks that the code doesn't have any spelling mistake.

6. `links_checker`

1. `links_checker`

This job ensures all links are valid in the documentation.

#### merge_test & scheduled pipeline

A scheduled pipeline is triggered at 8 pm each day to launch a full antivirus scan on each jobs. 

This pipeline triggers 3 jobs :  

This pipeline triggers 4 jobs :  

1. `refresh_job_av_database`   

Refresh antivirus definition's with `freshclam` command. See the [english documentation(https://help.ubuntu.com/community/ClamAV)(english) or [french documentation](https://doc.ubuntu-fr.org/clamav) for more information.

This job is only trigger when a branch is being merged or on a schedule pipeline. Iterates over the jobs to get their image and write a .gitlab-ci.yml that can run a child pipeline in order to use ClamAV for virus detection. The generated .gitlab-ci.yml is launched in the next job.

3. `child_job_av`   

It is launched by the previous job and scan the docker image and warn if they are know virus listed in the database.

4. `job_image_scan_schedule`

This job scans every image of the hub and warn if they are know vulnerability.

#### project_setup