Change "Merge when ready" text to "Enqueue" or "Add to merge queue"

I have a PR with all checks passing, but it shows "Merge when ready"

In other tools "Merge when ready" means "add to a queue when PR checks pass".

Here, it means "it will merge when it CI passes in the merge queue once you press this button enqueue it", which is a quite complex concept.

Can it be named "Add to a queue"?

先在 gh-stack 儲存庫中找到 "Merge when ready" 文字，並閱讀周圍的程式碼，以了解標籤定義的位置。將措辭改為要求的佇列術語，然後確認顯示的動作傳達的是將 pull request 加入佇列，而不是立即合併。

由索引模型根據 Issue 內容生成。