release 0.2 (xarray-contrib#131)

* add all missing changelog entries

* set the release date

* change the version

prepare for the release of `0.1.1` (xarray-contrib#109)

* release date

* touch up the changelog

* [skip-ci]

exclude bots from the release summary (xarray-contrib#105)

add pypipublish github action (xarray-contrib#29)