fix: add narwhals to conda recipe

[LiamConnors]

No description provided.

[emilykl]

@LiamConnors Under what circumstances is this meta.yaml file used? Is it just used by CI/development or by end users of Plotly.py?

[emilykl]

@LiamConnors Under what circumstances is this meta.yaml file used? Is it just used by CI/development or by end users of Plotly.py?

Answered offline, the meta.yaml specifies dependencies to install when using conda install.

Ideally IMO we should have just a single source of truth for dependencies so we don't need to update them in two places but in the meantime yes let's add narwhals in here to fix the conda installs.

[emilykl]

Note: build-doc step of the build CI is failing for a reason that seems unrelated to these changes — same failure is happening on master. @LiamConnors is investigating, but in the meantime I'm merging this branch anyway.