arguments sent to mermaid-cli.

Also expanded mermaid HTML element detection.

I used PyMdown Extension SuperFences for my Mermaid diagrams
in  MkDocs, so my HTML is still the old `<div class="mermaid">` blocks.
Therefore, I used regex to detect any HTML block with the `mermaid`
or `language-mermaid` class with at most one child HTML element.

…lement

mermaid_img_scale_reduction uses CSS height and width
to scale down the visual size of rendered mermaid diagrams.
This is a direct counter to puppeteer scale fed to
mermaid-cli so that setting both to the same
integer larger than 1 will result in a higher resolution
diagram at the natural 'scale 1' visual size.

…er application of additional CSS rules like 'width=100%'.

…age's style attribute if the image's attributes don't need to be fixed.