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

从 frameCount 的参考页面及对应的 content/references/translations/en/processing/frameCount.json 文件开始。跟踪参考页面的呈现方式，然后确定源链接应放置的位置；当参考页面提供指向此仓库中其源内容的直接链接时，工作就完成了。