Log Message:
(www/R-mathjaxr) Updated 1.4.0 t0 1.6.0

# mathjaxr 1.6-0 (2022-02-28)

* upgraded MathJax version to 3.2.0
* updated instructions for making use of the package
* fixed issue with `\mjeqn` coming first in a paragraph (issue #11)
* `preview_rd()` now shows links to local help pages (although they
  are non-functional) and displays figures (if there are any)