Allow specifying URLs for LaTeX engines

[ianqsong]

add a field for MathJax CDN that user can input by calling Documenter.HTML

Edit by @mortenpi: fix #1428

[mortenpi]

Thanks for the PR!

I think it would be more natural to handle all of it in the MathJax2/3 types. I.e. if you want to configure the URL, you'd just set something like HTML(mathengine = MathJax3(url="https://....")). No reason to add another global to the HTML struct. Beyond that:

• Docstrings would need to be updated to reflect the new arguments.
• It would be good to add a test to the example builds for overriding the URL, together with the relevant test in the tests file that would make sure that documenter.js contains the correct URL.

[ianqsong]

A new field url is added to MathJax2/3, of which the default value copies the original one, i.e., "cdnjs.cloudflare.com". So the tests file stays unchanged.

For such a small enhancement, I was wondering if one maintainer/committer could make it happen soon.

[mortenpi]

I took the liberty of modifying the tests a bit, to make sure we test all the cases. I would have two more requests before merging though:

1. Also add the same argument for KaTeX (for consistency).
2. Update the docstrings to reflect this argument

[ianqsong]

1. Also add the same argument for KaTeX (for consistency).

I don't have much knowledge of KaTax, but there are three urls

.../katex.min.css
.../katex.min.js
.../auto-render.min.js

Would you confirm that this is also the case for other CDNs?

I was thinking it be more efficient if I hand over this PR to you and you could do this in a single commit -- what'd you say?

[mortenpi]

I was thinking it be more efficient if I hand over this PR to you and you could do this in a single commit -- what'd you say?

I'm afraid that might not really be the case -- it's much less time-consuming just to review, so it would probably be a while before I get around to this in that situation.

Regarding KaTeX: you are right, I had forgotten that it was a bit more complicated. Let's leave KaTeX as it is.

[ianqsong]

docstrings is updated. Many thanks for your help with the test cases.

[mortenpi]

Thanks @ianqsong! I took the liberty of doing a few edits. Once the tests pass, this should be good to go.

[mortenpi]

@ianqsong was the closing of the PR accidental?

[ianqsong]

sorry, a fat-finger mistake