Contact form: Add a character count and increase height of text area (#583)

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[Preview](https://record-a-vac-contact-fo-aeruyy.herokuapp.com/contact-us)

Author: frankieroberto

app/views/contact-us.html

@@ -96,15 +96,17 @@ <h2 class="nhsuk-heading-m">Contact us</h2>
         items: items
       }) }}
 
-      {{ textarea({
+      {{ characterCount({
         name: "supportQuery",
         label: {
           text: "Details",
           classes: "nhsuk-label--s"
         },
         hint: {
           text: "Tell us more about the issue"
-        }
+        },
+        maxlength: 500,
+        rows: 10
       }) }}