Update challenges style guide to recommend triple backticks

docs/style-guide-for-curriculum-challenges.md

@@ -124,6 +124,15 @@ Here are specific formatting guidelines for challenge text and examples:
 - Language keywords go in `<code>` tags. For example, HTML tag names or CSS property names
 - The first instance of a keyword when it's being defined, or general keywords (i.e. "object" or "immutable") go in `<dfn>` tags
 - Single line code examples go in `<code>` tags
+- Multi-line code examples go between two sequences of triple backticks. Example:
+````
+```{language}
+
+[YOUR CODE HERE]
+
+```
+````
+The languages supported are listed [here](https://prismjs.com/#supported-languages)
 - Multi-line code examples go in `<blockquote>` tags, and use the `<br>` tag to separate lines. For HTML examples, remember to use escape characters to represent the angle brackets
 - A single horizontal rules (`<hr>` tag) should separate the text discussing the challenge concept and the challenge instructions
 - Additional information in the form of a note should be formatted `<strong>Note:</strong> Rest of note text...`