add Biomethanation

[BertoGBG]

Closes # (if applicable).

Changes proposed in this Pull Request

added biomethantion technology (biological methantion of CO2 with electrolytic H2). The technology is part of the DEA catalogue and it was added via compile_cost_assumptions.py

Checklist

• [ Y] Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• [ Y] Data source for new technologies is clearly stated.
• Newly introduced dependencies are added to environment.yaml (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• [Y ] I consent to the release of this PR's code under the GPLv3 license.