Automate skill label generation

## Problem
Skill labels need to be manually set up in `skills.json`. This
- increases manual work on the part of repo maintainers to ensure that the skills listed in a different repo (this one) are up to date
- causes redundancy of information that is already present in `cc-metadata.yml` under the `technologies` key in each repo

## Description
The technologies key could be expanded to a more verbose structure to describe languages, libraries and frameworks and then used to eliminate the need for `skills.json` entirely. This presents benefits such as
- richer information about the technological make-up of our projects
- automated sync of labels with technologies

## Alternatives
The improvements to `.cc-metadata.yml` can be a good-to-have part of the feature if there isn't a consensus to proceed with that. But the automation of skill labels is still beneficial. Also it does not have to be binary, a combination of `.cc-metadata.yml` and `skills.json` would also be a fine solution.

## Implementation

- [ ] I would be interested in implementing this feature.

Beginne damit, die aktuelle skills.json mit den Technologieeinträgen in der cc-metadata.yml jedes Repositorys zu vergleichen. Ermittle, ob das Feature skills.json ersetzen, die Metadaten erweitern oder beides kombinieren sollte, und definiere anschließend, wie Technologiedaten in synchronisierte Skill-Labels umgewandelt werden. Als erledigt gilt die Aufgabe, wenn Maintainer diese Labels nicht mehr manuell aktuell halten müssen.

Vom Indexierungsmodell aus dem Issue-Text verfasst.