Add Documentation for using single-dollar symbol for the KaTex (#2269)

* Add Documentation for using single-dollar symbol for the Katex

* xfi Katex to KaTex

* Revision pass and move to delimiters bullet

* Fix indentation, remove blank line

Co-authored-by: Erik Demaine <edemaine@mit.edu>
Co-authored-by: Ron Kok <ronkok@comcast.net>

docs/autorender.md

@@ -70,8 +70,8 @@ nodes inside this element and render the math in them.
 object passed to `katex.render`](https://github.com/KaTeX/KaTeX/#rendering-options),
 in addition to two auto-render-specific keys:
 
-- `delimiters`: This is a list of delimiters to look for math. Each delimiter
-  has three properties:
+- `delimiters`: This is a list of delimiters to look for math, processed in
+  the same order as the list. Each delimiter has three properties:
 
     - `left`: A string which starts the math expression (i.e. the left delimiter).
     - `right`: A string which ends the math expression (i.e. the right delimiter).
@@ -88,6 +88,19 @@ in addition to two auto-render-specific keys:
   ]
   ```
 
+  If you want to add support for inline math via `$...$`, be sure to list it
+  *after* `$$`, as in the following. (Because rules are processed in order,
+  putting a `$` rule first would catch `$$` as an empty math expression.)
+
+  ```js
+  [
+    {left: "$$", right: "$$", display: true},
+    {left: "$", right: "$", display: false},
+    {left: "\\(", right: "\\)", display: false},
+    {left: "\\[", right: "\\]", display: true}
+  ]
+  ```
+
 - `ignoredTags`: This is a list of DOM node types to ignore when recursing
   through. The default value is
   `["script", "noscript", "style", "textarea", "pre", "code", "option"]`.