zeripath 93df41f506
Fix slight bug in katex ()
There is a small bug in  whereby `$a a$b b$` will not be correctly
detected as a math inline block of `a a$b b`. This PR fixes this.

Also reenable test cases as per  

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
..
block_node.go Add KaTeX rendering to Markdown. ()
block_parser.go Add KaTeX rendering to Markdown. ()
block_renderer.go Add KaTeX rendering to Markdown. ()
inline_node.go Add KaTeX rendering to Markdown. ()
inline_parser.go Fix slight bug in katex ()
inline_renderer.go Add KaTeX rendering to Markdown. ()
math.go Add KaTeX rendering to Markdown. ()