feature: process html tags before markdown to latex conversion

[johnblommers]

This is really a documentation issue.

Normally writers using Markdown will include HTML tags to augment their formatting.

They may write π (π) or Ω (Ω) or → (→) or they may use an <img> tag to insert an image.

However simtex does not support translating HTML tags to their equivalent LaTeX representation. The result will be poor typographic representation when the user converts LaTeX to PDF, or worse, the converter will throw and error.

Consider making this clear to the user?

[iaacornus]

for now I think it should be considered clear to the user, but it is planned that it will support some of html tags in markdown, but not all, especially for better image formatting, since this gives more option to user compared to ![]()