Add Dependabot to help increase sustainability of project dependencies

[d33bs]

This comment is outside the bounds of this PR's focus. It might be a good idea for us to consider using Dependabot to help maintain the environment specifications for this project over time (esp. for Node and Python dependencies). uv-style pyproject.toml files aren't yet supported but likely will be in the future.

Originally posted by @d33bs in #47 (comment)