Website: Encourage usage of version 2

[pixelbrackets]

Steps to reproduce

• Open Website https://robo.li/
• Search installation guide

Expected behavior

• See installation command for latest version

Actual behavior

• See a instruction to edit the composer file manually (→ not recommended)
• See a instruction to use version 1 (→ legacy)

Suggested solution

Replace

Add to composer.json of your project

    require-dev: {
        "consolidation/robo": "^1.0.0"
    }

With

Install with [Composer](https://getcomposer.org/)

    composer require --dev consolidation/robo:^2.0

[pixelbrackets]

If the website source is available in a branch or another repository then I could provide a PR.