Add floating wind technology

[p-glaum]

Closes #36 but changed it to water depth below 60m

Changes proposed in this Pull Request

Add floating wind technology to PyPSA-Eur framework. Need to first update the technology data master with PR in https://github.com/PyPSA/technology-data/pull/108.

Checklist

• [x] I tested my contribution locally and it seems to work fine.
• [x] Code and workflow changes are sufficiently documented.
• [x] Changed dependencies are added to envs/environment.yaml.
• [x] Changes in configuration options are added in all of config.default.yaml.
• [x] Changes in configuration options are also documented in doc/configtables/*.csv.
• [x] A release note doc/release_notes.rst is added.