Standardized Naming of Topic Filenames

Topics appear in the natural order of the filenames, which do not necessarily coincide with the title.

• Find suitable format for Filenames, e.g. finite_sections_of_discrete_schroedinger_ops.md (see https://collaborating.tuhh.de/cfg0846/research-topics-mat-tuhh/-/wikis/Styleguide#naming-of-the-files)
• Adapt all existing files in /topics
• Adapt documentation

Further Info

Apparently, the ordering is also case-sensitive. It is therefore favorable to use lowercase letters for filenames.