DOC: improve docs for limited api builds - #885

Thanks @ngoldbaum for writing docs for the Limited API! Overall this content looks like a great start. My main comment right now is that it's not in the right places: it can't be in the reference guide, and the examples section of the "Passing arguments to Meson" page also feels wrong. I think we need a new page, as a how-to under "Using shared libraries" called something like "Using the Limited C API" or some such title.

This content, put together in a single page, will be a great start. I have a few things I'd like to add, like how to set it up as opt-in (e.g., as in PyWavelets/pywt#828).

We can then also address a couple of open issues: gh-624, some parts of gh-787.

Just a few quick remarks. I find the content in the new howto page hard to read, mostly because there are things repeated several times with different language and because the content is not presented at increasing level of detail but zooming in and out constantly. The other are minor comments. Please squash the commits into just one commit.

This is looking pretty good. A couple more suggestions to give the desired recommendations to users.

Thanks. This looks very nice. A few more comments.

Thanks Nathan. Very close, two more comments from me.

This looks great to me now. I checked and resolved all open comments. I've already been pointing people at these docs, so I'll merge this in a few days unless there are more comments.