redirect renamed/outdated .md files

[Svanvith]

We need an option to redirect outdated or renamed files.

Docusaurus has an option:

https://docusaurus.io/docs/api/plugins/@docusaurus/plugin-client-redirects

[schweigisito]

This has been done meanwhile, hasn't it? IRC this was part of #461 and has been released in #460

[schweigisito]

@Svanvith, I am "empowering" myself and closing it :-)