Pyproject doc link fix

[MaximilianMeiler]

Poetry won't install properly if no link exists in the toml file. I've linked it to what is also placed on the repo.

Overview: What does this pull request change?

This just adds a link to the manim-dsa documentation in the pyproject.toml file - I found that my poetry wouldn't work without it, and figured it might be a common issue for future installs.

Reviewer Checklist

• [ ] The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• [ ] If applicable: newly added code segments are adequately covered by tests
• [ ] If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section

[MaximilianMeiler]

That link actually points to the documentation of the project we forked and the functionality has diverged from this project. I would recommend using the official Manim documentation instead as we do not have an official documentation yet. https://docs.manim.community/en/stable/

This should hopefully now be fixed ^