Fix #9864: mathjax: Failed to render equations via MathJax v2

[tk0miya]

Feature or Bugfix

• Feature
• Bugfix

Purpose

• MathJax library has been loaded via "defer" strategy since v4.3.0. But
  it prevents to work MathJax v2. This rollbacks the change and use
  "async" strategy as default again.
• To support changing "defer" strategy, this introduces a new confval;
  mathjax_loading_method to switch the loading method of MathJax.
• refs: Add option to choose mathjax load method #9864

[mgeier]

Is it really necessary to add a new config value for this?

What about allowing users to specify

mathjax_options = {'async': 'async'}

?

The logic in the implementation would have to change like this: add 'defer': 'defer' to the options, but only if they don't already contain 'async': 'async'. That seems straightforward to me, or am I missing something?

[mgeier]

It's probably better to check if the config_options contain either of the keys 'async' or 'defer', and only add 'defer': 'defer' if none of those keys is available (regardless of their values).

[tk0miya]

It's a good idea.

It's probably better to check if the config_options contain either of the keys 'async' or 'defer', and only add 'defer': 'defer' if none of those keys is available (regardless of their values).

My thought is the default setting should be "async" during v4.x to keep compatibility.