Provide structured API documentation generated from docstrings

objects.inv exists, what does not exist is the API reference documentation.

I took some time to look into this, and Adrián has summarized the problem well. The use of intersphinx to check references implies the existence of targets for any reference you might make--basically, API reference documentation--and that's not how the Beautiful Soup documentation is written. Sphinx syntax does not allow me to just drop in targets where appropriate. These targets become section headings rendered with special formatting, and adding them requires changes to the text and structure of the documentation.

I was able to rewrite the documentation such that it contains intersphinx targets for the classes most likely to be mentioned in other projects' documentation. It reads a little bit awkward, but it might be worth using in the short term. In the long term, the documentation needs to be rearchitected with the two parts that are now traditional for open source software projects: a narrative guide and a structured set of API documentation automatically generated from docstrings.

After putting out the 4.12.0 release I updated the documentation to include the intersphinx targets. I tested it out with a test document that looks like this:

Intersphinx test documentation for Beautiful Soup
=================================================

* A class: :py:class:`bs4.BeautifulSoup`
* Another class: :py:class:`bs4.Tag`
* An attribute: :py:attr:`bs4.Tag.name`

In conf.py for the test project, my intersphinx_mapping looks like this:

intersphinx_mapping = {
    "beautifulsoup4": (
        "https://www.crummy.com/software/BeautifulSoup/bs4/doc/", None
    )
}

Leaving this issue open pending a better long-term solution.