adds in aria attributes and semantic status content for chem eq problems

common/lib/capa/capa/templates/chemicalequationinput.html

@@ -11,13 +11,13 @@
     <div class="incorrect" id="status_${id}">
     % endif
 
-    <input type="text" name="input_${id}" id="input_${id}" data-input-id="${id}" value="${value|h}"
+    <input type="text" name="input_${id}" id="input_${id}" aria-describedby="answer_${id}" data-input-id="${id}" value="${value|h}"
    % if size:
    size="${size}"
    % endif
    />
 
-      <p class="status">
+      <p class="status" aria-describedby="input_${id}">
         % if status == 'unsubmitted':
         unanswered
         % elif status == 'correct':