DOC: Add entry to pandas extension list

[mocquin]

Pandas version checks

• I have checked that the issue still exists on the latest versions of the docs on main here

Location of the documentation

https://pandas.pydata.org/docs/ecosystem.html#ecosystem-extensions

Documentation problem

I worked on an extension to the physipy package, that allows handling physical units. The extension provides dtype and accessor.
The extension is packaged in physipandas.

As suggested in the doc, I propose to add the project to the documentation.
Notice that the target package, physipy, aims kind of the same goals as pint, that is already in the extension list.

Suggested fix for documentation

Add an entry to https://pandas.pydata.org/docs/ecosystem.html#ecosystem-extensions for the extension, and to https://pandas.pydata.org/docs/ecosystem.html#accessors for the accessor registered as df.physipy..

[jbrockmendel]

PR welcome

[nidhiiiiii]

can i take up this issue as my first contribution?

[krishh16]

take

[krishh16]

@mocquin what do i have to add in the classes column while adding it in the docs? Series of DataFrame?

[rsm-23]

Taking up this stale PR. Hope that's fine.

[rsm-23]

take

[rsm-23]

@jbrockmendel can you please take up the PR review?