Has a developer I would like to create a contentset via aio cli

**Is your feature request related to a problem? Please describe.**
Currently with aio cli we can get or delete a contentset, but I don't see a way to create the content set with the command line

**Describe the solution you'd like**
As the API allow to create a contentset, it should be possible to implement it in the aio cli

**Describe alternatives you've considered**
I don't see any alternative.

**Additional context**
I need to create quickly a contentset based on some diff tool report in order to speed up what need to be re-sync.

まず、contentsetを取得および削除する既存のaio CLIコマンドを調べ、次にそれらをAPIのcontentset作成操作と比較します。完了の条件は、CLIがそのAPIで必要とされる情報からcontentsetを作成でき、報告されたdiff-toolワークフローをサポートすることです。

索引モデルが issue の本文から書いたものです。