Create an MSRV policy in this crate

TLDR woudl be:
1. Define a MSRV policy (maybe copy the existing DataFusion one)
2. Implement some sort of CI check (again can copy / reuse the datafusion one if we want)
3.

🤔 interestingly we don't seem to have an MSRV policy in this crate (at least not that I could find in https://github.com/apache/datafusion-sqlparser-rs/blob/main/README.md)

We do have such a thing in DataFusion here: https://github.com/apache/datafusion?tab=readme-ov-file#rust-version-compatibility-policy

Maybe it is worth considering adding some documentation / policy in the sqlparser crate too 🤔

_Originally posted by @alamb in https://github.com/apache/datafusion-sqlparser-rs/issues/1736#issuecomment-2676808035_

先比較此 crate 的 README 與 DataFusion 的 Rust 版本相容性政策，然後檢視 issue 所參照的現有 DataFusion CI 檢查。定義此 crate 的 MSRV 政策，將其記錄在 README 中，並新增一項強制執行所選相容性層級的 CI 檢查。

由索引模型根據 Issue 內容生成。