v1.2.4

Agents:

• Add hello_world skill and agent

Docs:

• Update repository documentations
• Update installation guide for Raspberry Pis (add a link to prebuilt image for Raspberry Pis)

Misc:

• Update the dependencies (protobuf, jsonschema, cosmpy)
• Various improvements in the repository structure (e.g. makefile, tox, workflows)
• Speed up CI/CD
• Various bug fixes