Update MD009/no-trailing-spaces with code_blocks parameter to allow reporting/fixing trailing spaces in indented/fenced code blocks (fixes #1181).

doc-build/md009.md

@@ -1,21 +1,19 @@
 This rule is triggered on any lines that end with unexpected whitespace. To fix
 this, remove the trailing space from the end of the line.
 
-Note: Trailing space is allowed in indented and fenced code blocks because some
-languages require it.
-
 The `br_spaces` parameter allows an exception to this rule for a specific number
 of trailing spaces, typically used to insert an explicit line break. The default
-value allows 2 spaces to indicate a hard break (\<br> element).
+value allows 2 spaces to indicate a hard break (\<br> element). (You must set
+`br_spaces` to a value >= 2 for this parameter to take effect. Setting
+`br_spaces` to 1 behaves the same as 0, disallowing any trailing spaces.)
 
-Note: You must set `br_spaces` to a value >= 2 for this parameter to take
-effect. Setting `br_spaces` to 1 behaves the same as 0, disallowing any trailing
-spaces.
+By default, trailing space is allowed in indented and fenced code blocks because
+some programming languages require that. To report such instances, set the
+`code_blocks` parameter to `true`.
 
 By default, this rule will not trigger when the allowed number of spaces is
 used, even when it doesn't create a hard break (for example, at the end of a
-paragraph). To report such instances as well, set the `strict` parameter to
-`true`.
+paragraph). To report such instances, set the `strict` parameter to `true`.
 
 ```markdown
 Text text text