Support of new Syntax

Hello,

a project of the company I am working for, requires a high performance SQL parser such as this one. However, we would mainly require the [Exasol](https://www.exasol.com/) syntax (which is a lot like Oracle syntax) and we may also need DB2 (z/OS and LUW) syntax.

We are considering and willing to implement the needed syntax and would love to officially contribute that syntax here and share it with the community. But before we start working on it, we have to check our internal policies, whether we are allowed to do so or not. Furthermore, we would like to ask you as well for your opinion on this, since Exasol is not a very popular or widespread RDBMS and the readme specifically states the following:
> The most commonly accepted PRs add support for ... a **popular** RDBMS ... will likely be accepted after a brief review.

We want to make sure, that our contribution would be be accepted and supported (being reviewed) by the responsible contributors of this project (of course only if it meets all the standards and contribution guidelines).

I am looking forward to a hopefully positive reply!

該 issue 沒有列出檔案、測試或進入點。先閱讀 README 中關於語法支援和貢獻的指南，然後檢視目前如何表示各個方言，再與維護者討論 Exasol 和 DB2 的範圍。Done 要求達成共識的範圍和獲接受的實作計畫，而不只是修改 parser。

由索引模型根據 Issue 內容生成。