add maintenance note regarding #10864's addition

getting-started.html

@@ -64,6 +64,8 @@ base_url: "../"
     <p class="lead">Within the download you'll find the following directories and files, logically grouping common resources and providing both compiled and minified variations.</p>
     <p>Once downloaded, unzip the compressed folder to see the structure of (the compiled) Bootstrap. You'll see something like this:</p>
 
+<!-- NOTE: This info is intentionally duplicated in the README.
+Copy any changes made here over to the README too. -->
 {% highlight bash %}
 bootstrap/
 ├── css/