Electrolyzer grid connection costs - US data

[danielelerede-oet]

Changes proposed in this Pull Request

This PR includes grid connection costs to electrolyzers' investment costs in US data.

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• 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.
• I consent to the release of this PR's code under the GPLv3 license.

[euronion]

Thanks for the PR @danielelerede-oet .

1. Can you make it more clear where the grid connection costs are coming from? I tried searching for the term grid connection in the linked source documents without success. A page number or at least the original number taken from the sources would go a long way.

2. Are those grid connection costs are only relevant grid connected units, or do they also include BOP costs? The questions aims to whether you want to add the costs on top of the existing entry, or whether you want to create a separate entry e.g. for grid connection costs for electrolysers, to keep the info separate. That would allow models in the future to also model islanded units.