adding version 1.3.0 to docs

[shimwell]

Description

This PR adds version 1.3.0 to the drop down menu in the online docs

Checklist

• I'm making a PR from a feature branch on my fork into GEOUNED-org/GEOUNED/dev branch
• I have followed PEP8 style guide for Python or run a formatter such as black or ruff format on my code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works

[shimwell]

@AlvaroCubi perhaps this documentation for version 1.3.0 could be merger in. I noticed 1.4.0 was just release so we could do with updating the docs