[Enh]: str zfill

[williambdean]

We would like to learn about your use case. For example, if this feature is needed to adopt Narwhals in an open source project, could you please enter the link to it below?

I would like to use narwhals for the latent-calendar project. However, it uses zfill

https://github.com/williambdean/latent-calendar/blob/07ffd832188098af21a469470bb988560d7b6e80/latent_calendar/transformers.py#L155

Please describe the purpose of the new feature or describe the problem to solve.

pad a string

Suggest a solution if possible.

use the pandas, polars, spark, etc functionality

If you have tried alternatives, please describe them below.

looked through the docs

Additional information that may help us understand your needs.

No response

[MarcoGorelli]

defo in scope, thanks for the request!

[williambdean]

Amazing. I am happy to contribute as well

[MarcoGorelli]

sure that would be great! check CONTRIBUTING.md for how to get started