Add autocomplete for operator

To avoid mistakes it would be great to have operator autocomplete in types.

We could either just use a union type and then allow also for any string to account for custom operators, or we could be strict and pair each operator with its corresponding value (e.g. `lessThan` needs a `value: number`, and we could document them so users know how to extend that with their custom types.

If there is interest in this I'd be happy to contribute the PR.

Thanks in advance.

從 issue 提案開始，檢查 repository 中現有的型別定義和運算子處理方式。比較提議的基於 union 的自動完成與成對的運算子/值型別，包括應如何擴充自訂運算子。完成的標準是：所選設計提供運算子自動完成，並清楚記錄自訂型別。

由索引模型根據 Issue 內容生成。