document fenced_code_attributes extension

Adds explanation of this extension to the README, using
description provided in 7654db9df1b68926371da2a1f23db6df93056f44.

1 files changed, 7 insertions, 0 deletions

diff --git a/README b/README
index a469b8c9c..bc80f1b5a 100644
--- a/README
+++ b/README
@@ -1181,6 +1181,8 @@ row of tildes or backticks at the start and end:
     ~~~~~~~~~~
     ~~~~~~~~~~~~~~~~
 
+**Extension: `fenced_code_attributes`**
+
 Optionally, you may attach attributes to the code block using
 this syntax:
 
@@ -1217,6 +1219,11 @@ This is equivalent to:
     qsort [] = []
     ```
 
+If the `fenced_code_attributes` extension is disabled, but
+input contains class attribute(s) for the codeblock, the first
+class attribute will be printed after the opening fence as a bare
+word.
+
 To prevent all highlighting, use the `--no-highlight` flag.
 To set the highlighting style, use `--highlight-style`.