feat: Create a new Admin panel based on DecapCMS

Description

Install a DecapCMS to edit cards & links contents. features:

• gitlab authentication ;
• edit/create/delete existing cards & links ;
• Update settings.json on yo

Out of Scope:

• images

Issues :

Checklist before merge :

• No remaining console.log
• Version changed if new feature
• Lint ok
• all eslintConfig rules are on ("2") (except no-useless-escape / vue/no-mutating-props)
• Test aktivisda and backtivisda
• Implement new features on yo

Tests

• Tests are ok
• If it’s a bug, a new test added
• If it’s a new feature, a new test added