Update links for python v0.5 - #61

Detected 6 broken links. docs/index.md [404] docs/model-library/index.md docs/tutorials/treeppl-intro.md [404] courses/treeppl-tutorial.pdf [404] courses/basic-tutorial.zip [404] courses/basic-tutorial-solutions.zip docs/tutorials/pigeons.md [404] docs/model-library/diversification.md docs/changelog.md [500] https://github.com/miking-lang/miking-dppl/pull/242

[500] https://github.com/miking-lang/miking-dppl/pull/242

[404] docs/model-library/diversification.md

[404] courses/basic-tutorial-solutions.zip

[404] courses/basic-tutorial.zip

[404] courses/treeppl-tutorial.pdf

[404] docs/model-library/index.md

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, JustinBeckwith/linkinator-action@v1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/