Adding "Go to source" link to reference pages

Which area of the website does this enhancement relate to?

Reference

Describe the enhancement

Reference pages don't have any reference, connecting them to their source version in this repo. Let's say you want update a reference page, or simply fix a typo: https://processing.org/reference/frameCount.html While the change is only a single letter, because the website has no reference to https://github.com/processing/processing-website/blob/1fce63d07182becca614b95ab76b3b1416424d8d/content/references/translations/en/processing/frameCount.json , one should learn where the content is kept and search for the content in the repo.

Why is this enhancement important?

The lack of direct connection the presentation and source layer for reference docs makes the contribution process harder.

Additional context

No response

frameCount のリファレンスページと、それに対応する content/references/translations/en/processing/frameCount.json ファイルから始めます。リファレンスページがどのように表示されているかをたどり、次にソースへのリンクをどこに配置すべきかを判断します。リファレンスページからこのリポジトリ内のソースコンテンツへの直接リンクが提供されれば、作業は完了です。