[Enh]: Extend signature of supported methods

[FBruzzesi]

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?

No response

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

There are some methods for which we have partial support, meaning that not the full polars api is supported.

However this should be possible for some methods and/or some arguments (examples below)

Suggest a solution if possible.

No response

If you have tried alternatives, please describe them below.

No response

Additional information that may help us understand your needs.

Here a (partial) list of methods and arguments missing:

method	missing argument(s)	note
DataFrame.drop	strict	✅ Fixed in #773
DataFrame.drop_nulls	subset	✅ Fixed in #779
DataFrame.join	suffix	✅
DataFrame.join_asof	suffix, tolerance

[MarcoGorelli]

cool, happy to expand where it makes sense - if it's possible to get support across pandas/polars/pyarrow then it's probably already worth doing!

[FBruzzesi]

Closing this for now, we can come back to join_asof and other methods when and if required for adoption