Improve highlighting of code samples

SC1039.md

@@ -5,9 +5,9 @@
 ```sh
 for f in *.png
 do
-  cat << EOF
+  cat << HTML
      <img src="$f" /><br/>
-  EOF
+  HTML
 done > index.html
 ```
 
@@ -16,11 +16,12 @@ done > index.html
 ```sh
 for f in *.png
 do
-  cat << EOF
+  cat << HTML
      <img src="$f" /><br/>
-EOF
+HTML
 done > index.html
 ```
+
 ### Rationale:
 
 The here document delimiter will not be recognized if it is indented.
@@ -34,4 +35,4 @@ Removing the indentation is preferred, since the script won't suddenly break if
 
 ### Exceptions:
 
-If the line was supposed to be a literal part of the here document, consider choosing a less ambiguous token.
+If the line was supposed to be a literal part of the here document, consider choosing a less ambiguous token.