* Markdown: Let WikiText parsing handle the creation of LaTeX widgets.
When embedding LaTeX snippets in inline HTML nodes, such as TiddlyRemember
macros or HTML tables, the parsing of latex nodes breaks the WikiText by
splitting it into pieces around the latex node.
This commit fixes the issue by converting the Remarkable katex nodes back to
text, using a newline to indicate a block katex snippet. This is then re-parsed
by the WikiText KaTeX plugin.
TESTED:
Created a test wiki with:
```
$ node tiddlywiki.js test --init markdowndemo
$ node tiddlywiki.js test --listen
```
* Verified markdown + KaTeX support still works as expected.
* Verified that embedding LaTeX snippets in inline HTML works (e.g. `<a
href="https://example.com/">$x^2$</a>`).
* Verified the markdown + KaTeX support works as expected with renderWikiText
set to `false`.
* Style: Remove spaces between if and opening parentheses.
