Log Message:
tex-make4ht{,-doc}: update to 0.3g

New features:
- new extension: `mjcli`. It uses command line MathJax to convert math in
  MathML or LaTeX syntax to HTML. The generated HTML doesn't need any
  JavaScript to display math in web browsers. It replaces the older extension
  `mathjaxnode`, which uses a deprecated version of command line MathJax, and
  doesn't support the LaTeX input.
- exit status is now set, so it is possible to test if the compilation ran
  without errors in scripts.

Bug fixes:
- fixed handling of nested `<span>` elements in `joincharacters` filter.
- generate YAML header for all produced HTML files in `staticsite` extension.
- various fixes for the MathML output.