fix(auto-render): strict dollar delimiter

[taufik-nurrohman]

What is the previous behavior before this PR?

The dollar delimiter, especially the non-display version, is disabled by default because it often causes errors in determining the boundary when there are at least two numbers followed by the $ symbol present in one paragraph.

What is the new behavior after this PR?

This change makes it possible to make the delimiter stricter in determining the math boundary, by checking what characters come before the opening delimiter and what characters come after the closing delimiter.

Tests

Tests are available as follows:

<ul>
  <li>$E=mc^2$</li>
  <li>$E=mc^2$asdf</li>
  <li>asdf$E=mc^2$</li>
  <li>asdf$E=mc^2$asdf</li>
  <li>$E=mc^2$ asdf</li>
  <li>asdf $E=mc^2$</li>
  <li>asdf $E=mc^2$ asdf</li>
  <li>($E=mc^2$)asdf</li>
  <li>asdf($E=mc^2$)</li>
  <li>asdf($E=mc^2$)asdf</li>
  <li>asdf asdf 20$ asdf 30$ asdf asdf asdf</li>
  <li>asdf asdf $20 asdf $30 asdf asdf asdf</li>
  <li>asdf asdf $20 asdf 30$ asdf asdf asdf</li>
  <li>asdf asdf 20 $ asdf 30 $ asdf asdf asdf</li>
  <li>asdf asdf $ 20 asdf $ 30 asdf asdf asdf</li>
  <li>asdf asdf $ 20 asdf 30 $ asdf asdf asdf</li>
</ul>

<ul>
  <li>$$E=mc^2$$</li>
  <li>$$E=mc^2$$asdf</li>
  <li>asdf$$E=mc^2$$</li>
  <li>asdf$$E=mc^2$$asdf</li>
  <li>$$E=mc^2$$ asdf</li>
  <li>asdf $$E=mc^2$$</li>
  <li>asdf $$E=mc^2$$ asdf</li>
  <li>($$E=mc^2$$)asdf</li>
  <li>asdf($$E=mc^2$$)</li>
  <li>asdf($$E=mc^2$$)asdf</li>
  <li>asdf asdf 20$$ asdf 30$$ asdf asdf asdf</li>
  <li>asdf asdf $$20 asdf $$30 asdf asdf asdf</li>
  <li>asdf asdf $$20 asdf 30$$ asdf asdf asdf</li>
  <li>asdf asdf 20 $$ asdf 30 $$ asdf asdf asdf</li>
  <li>asdf asdf $$ 20 asdf $$ 30 asdf asdf asdf</li>
  <li>asdf asdf $$ 20 asdf 30 $$ asdf asdf asdf</li>
</ul>

<ul>
  <li>asdf +10$ asdf -10$ asdf</li>
  <li>asdf +10 $ asdf -10 $ asdf</li>
  <li>asdf $+10 asdf $-10 asdf</li>
  <li>asdf $ +10 asdf $ -10 asdf</li>
</ul>

<ul>
  <li>asdf +10.5$ asdf -10.5$ asdf</li>
  <li>asdf +10.5 $ asdf -10.5 $ asdf</li>
  <li>asdf $+10.5 asdf $-10.5 asdf</li>
  <li>asdf $ +10.5 asdf $ -10.5 asdf</li>
</ul>

<ul>
  <li>asdf +10,5$ asdf -10,5$ asdf</li>
  <li>asdf +10,5 $ asdf -10,5 $ asdf</li>
  <li>asdf $+10,5 asdf $-10,5 asdf</li>
  <li>asdf $ +10,5 asdf $ -10,5 asdf</li>
</ul>

<ul>
  <li>asdf +10,000,000.5$ asdf -10,000,000.5$ asdf</li>
  <li>asdf +10,000,000.5 $ asdf -10,000,000.5 $ asdf</li>
  <li>asdf $+10,000,000.5 asdf $-10,000,000.5 asdf</li>
  <li>asdf $ +10,000,000.5 asdf $ -10,000,000.5 asdf</li>
</ul>

<ul>
  <li>asdf +10.000.000,5$ asdf -10.000.000,5$ asdf</li>
  <li>asdf +10.000.000,5 $ asdf -10.000.000,5 $ asdf</li>
  <li>asdf $+10.000.000,5 asdf $-10.000.000,5 asdf</li>
  <li>asdf $ +10.000.000,5 asdf $ -10.000.000,5 asdf</li>
</ul>

<ul>
  <li>asdf1234$E=mc^2$</li>
  <li>asdf1234$E=mc^2$1234asdf</li>
  <li>$E=mc^2$1234asdf</li>
  <li>asdf1234 $E=mc^2$</li>
  <li>asdf1234 $E=mc^2$ 1234asdf</li>
  <li>$E=mc^2$ 1234asdf</li>
</ul>

Fixes #1202