Adding "Go to source" link to reference pages

[ulgens]

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

[ulgens]

Coming from #699, it seems frameCount.json file wasn't even the write source. I still don't know what is the source of truth for doc, and I think it shows why having a "go to source" button is important 😬