Add CustomSql analyzer

Hi all,
Thanks for maintaining this library — it's been very helpful for our data quality project. I would like to propose adding a CustomSql analyzer.

**Is your feature request related to a problem? Please describe.**
The Python version of PyDeequ currently lacks support for the `CustomSql` analyzer available in the Scala version, I could use one on the current data quality project im working on.

**Describe the solution you'd like**
Add a Python wrapper for the existing `CustomSql` analyzer from the Scala implementation.

**Describe alternatives you've considered**
I can't think of any alternatives. The functionality already exists in Scala, and this feature would simply expose it to Python

**Additional context**
I've submitted a pull request with the proposed implementation. Feedback and suggestions are welcome!

まず、Python の analyzer wrapper と既存の Scala CustomSql analyzer を比較し、次に Python API が Scala analyzer をどのように公開しているかを調べます。CustomSql が Python API 経由で利用可能になり、Scala 実装と一致する動作をし、関連するテストがパスすれば完了です。

索引モデルが issue の本文から書いたものです。