Make logo image in README.md link to documentation

[Tanmay692004]

Clicking the logo image on the documentation launches the website in another tab

Description

The logo has been updated to be clickable and opens the Gymnasium-Robotics website in a new tab when clicked. This change improves navigation by allowing users to visit the website without leaving the current page.

Type of change

• Documentation only change (no code changed)

Screenshots

Before

After

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[Kallinteris-Andreas]

Thanks for this pull request, both in gymnasium and gymnasium robotics.