Task: improve the "Using issue tracker" section

The Using issue tracker page seems to describe how to use issue tracker for people who want to report a bug and how to help triage issue.

Seeing this is the developer's guide (aka contributing to Python guide), it would be great if there are sections dedicated for how to search for issues to start contributing.
Even the section about what each fields in the issue tracker mean, perhaps it can be moved outside of the "triaging" section. Those info are useful for general contributors too, not just for triagers. A first time contributor might decide to skip that section entirely, because they don't have triage role, and therefore missing out important information.

從 devguide.python.org/tracker/ 的 Using issue tracker 頁面以及 triaging 頁面中的 Fields in the issue tracker 部分開始。檢視貢獻者目前如何尋找 issue，並決定欄位說明應放在哪裡。當指南包含面向貢獻者的 issue 搜尋指引，且不在 triaging 中也能找到欄位資訊時，即視為完成。