docs: Document configuration of the remark-math plugin

Author: waldyrious

website/docs/guides/markdown-features/markdown-features-math-equations.mdx

@@ -75,7 +75,6 @@ Enable KaTeX:
     import rehypeKatex from 'rehype-katex';
     // highlight-end
 
-    // highlight-start
     export default {
       presets: [
         [
@@ -188,6 +187,52 @@ export default {
 
 </details>
 
+## Using double dollar signs as delimiters
+
+In some cases (e.g. prose that includes prices in dollars), it may be undesirable to treat any pair of single dollar signs occurring in the same line as delimiters of math syntax. To configure the plugin to only recognize double dollar signs as delimiters of inline math, set the option set the [`singleDollarTextMath` configuration option]() to `false`:
+
+```js title="docusaurus.config.js"
+export default {
+  presets: [
+    [
+      '@docusaurus/preset-classic',
+      {
+        docs: {
+          path: 'docs',
+          // highlight-start
+          remarkPlugins: [[remarkMath, {singleDollarTextMath: false}]],
+          // highlight-end
+          rehypePlugins: [rehypeKatex],
+        },
+      },
+    ],
+  ],
+};
+```
+
+This will allow writing markdown like:
+
+```latex
+The item costs $300 but is available at a discounted rate of $290.
+The absolute difference is $$\$300 - \$290 = \$10$$, and the relative difference, as a percentage, is given by:
+
+$$$
+\left(1 - \frac{290}{300} \right) \times 100 \approx 3.33 \%
+$$$
+```
+
+with the results being:
+
+<BrowserWindow>
+
+The item costs \$300 but is available at a discounted rate of \$290. The absolute difference is $$\$300 - \$290 = \$10$$, and the relative difference, as a percentage, is given by:
+
+$$
+\left(1 - \frac{290}{300} \right) \times 100 \approx 3.33 \%
+$$
+
+</BrowserWindow>
+
 ## Self-hosting KaTeX assets {#self-hosting-katex-assets}
 
 Loading stylesheets, fonts, and JavaScript libraries from CDN sources is a good practice for popular libraries and assets, since it reduces the amount of assets you have to host. In case you prefer to self-host the `katex.min.css` (along with required KaTeX fonts), you can download the latest version from [KaTeX GitHub releases](https://github.com/KaTeX/KaTeX/releases), extract and copy `katex.min.css` and `fonts` directory (only `.woff2` font types should be enough) to your site's `static` directory, and in `docusaurus.config.js`, replace the stylesheet's `href` from the CDN URL to your local path (say, `/katex/katex.min.css`).