DOC: example for doing a reversed rolling window

[jreback]

#34226 (comment) is the example, should just add to window.rst

also would be good to show using https://pandas.pydata.org/pandas-docs/dev/reference/api/pandas.api.indexers.FixedForwardWindowIndexer.html?highlight=forward#pandas.api.indexers.FixedForwardWindowIndexer

[MaruthiKo]

Dear Developer,
I am new to open source contributions and I would like to contribute. Can someone pls help me up with how and where do I start?

[mzeitlin11]

Hi @MaruthiKo, welcome to pandas! I'd recommend reading https://pandas.pydata.org/docs/development/contributing.html for guidance on contribution to pandas. If you'd like to work on this issue, the Contributing to the documentation section should be particularly useful.

[vangorade]

looks like issue is still not resolved let me fix it real quick.

[vangorade]

take

[hvp004]

Is this available to take? I see no updates in almost 2 months.

[mdhsieh]

I can make suggested changes from the closed pull request.

[mdhsieh]

take