Adding polle package

[kkholst]

The polle package provides a unified framework for policy learning in R and implements both new methods and wraps methods from other R packages, which makes the different policy learning methods much more user friendly.
The package is described in details here: https://arxiv.org/abs/2212.02335.

[zeileis]

Julie @julierennes, Nick @NickCH-K, Pan @panzhaooo, this has been open for a while and it would be good to follow up in some way. The paper is also about to be published in the Journal of Statistical Software and it would be nice to know whether the paper can mention that the package is on the task view or not.

Given that the PR was made so long ago, there are conflicts now. Either you have to resolve the conflicts or simply close the PR and add the paragraph about the package directly in the main branch.

[NickCH-K]

Added this package with 77db3f8

[zeileis]

Thanks, Nick @NickCH-K !