More fields in @doc-json

[dlesbre]

As mentioned in the discuss.ocaml post, I would appreciate a few extra fields in the generated JSON files to make integrating them in my website easier. jonludlam suggested I open an issue for these here as well:

• A title field with the page title (currently obtainable from breadcrumbs[-1].name
• A package field with the name of the current package (currently can be obtained from the path of the generated doc)
• A version field with the version of the current package (I'm building versioned docs). Currently I can only obtain this through git ref names.
• An objects fields with the list and type (val, module, type, module type...) of all objects defined in the current file
• A sherlodoc field indicating whether or not sherlodoc was present (and if so, the relative path from the current file to the db.js file).

[AllanBlanchard]

I don't know if it is entirely related, but this news:

https://tarides.com/blog/2024-02-28-two-major-improvements-in-odoc-introducing-search-engine-integration/

Suggests that the DB exists in Json, would it be possible to get it? The main problem with the db.js files is that if you have several packages in your project, the search engine does not merge all packages at top-level.