Expand docs with batching example

Add a short doc on the use of `BatchSQLAlchemyConnectionField` with a brief comment. It's only documented in the test files, but should also be included in the documentation.

Additionally, can expand docs on `sort` keyword to include disabling and custom usage.

_Originally posted by @palisadoes in https://github.com/graphql-python/graphene-sqlalchemy/issues/357#issuecomment-1447481010_

先找到記錄 BatchSQLAlchemyConnectionField 的測試檔案，以及關於 sort 關鍵字的現有文件。加入一個附有簡短註解的批次處理範例，然後記錄如何停用 sort 以及如何使用自訂排序。專案文件涵蓋這兩個主題，且相關的文件檢查通過後，即表示完成。

由索引模型根據 Issue 內容生成。