Exclude draft time

- pull_request has timelineItems: https://docs.github.com/en/graphql/reference/objects#pullrequest
- we should filter timelineItems to fetch only PullRequestReadyForReview events: https://docs.github.com/en/graphql/reference/objects#readyforreviewevent

找出取得 timelineItems 的 pull_request 查詢，並檢視 issue 中連結的 GitHub GraphQL PullRequest 與 ReadyForReviewEvent 文件。更新 timeline 篩選邏輯，僅取得 PullRequestReadyForReview 事件，以排除處於 draft 狀態的時間；接著確認產生的分析是否以 ready-for-review 事件作為起點。

由索引模型根據 Issue 內容生成。