fix(banner): fix issue with classes not working if banner type provided

src/moj/components/banner/template.njk

@@ -1,4 +1,28 @@
-<div class="moj-banner{% if params.type == 'success' %} moj-banner--success{% elif params.type == 'warning' %} moj-banner--warning{% else %} {{- ' ' + params.classes if params.classes}}{% endif %}" {%- for attribute, value in params.attributes %} {{ attribute }}="{{ value }}"{% endfor %} role="region" aria-label="{{ params.iconFallbackText | default(params.type) | default("banner") }}">
+{#- Set classes for this component #}
+{%- set classNames = ["moj-banner"] -%}
+
+{%- if params.type == 'success' %}
+  {%- set classNames = classNames.concat("moj-banner--success") %}
+{%- elif params.type == 'warning' %}
+  {%- set classNames = classNames.concat("moj-banner--warning") %}
+{%- elif params.type == 'information' %}
+  {%- set classNames = classNames.concat("moj-banner--information") %}
+{%- endif %}
+
+{%- if params.classes %}
+  {%- set classNames = classNames.concat(params.classes) %}
+{%- endif %}
+
+{%- set classNames = classNames | join(' ') -%}
+
+<div 
+  class="{{ classNames }}" 
+    {%- for attribute, value in params.attributes %} 
+      {{ attribute }}="{{ value }}"
+    {% endfor %}
+  role="region"
+  aria-label="{{ params.iconFallbackText | default(params.type) | default("banner") }}"
+>
 
   {% if params.type == 'success' %}
     <svg class="moj-banner__icon" fill="currentColor" role="presentation" focusable="false" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 25 25" height="25" width="25"><path d="M25,6.2L8.7,23.2L0,14.1l4-4.2l4.7,4.9L21,2L25,6.2z"/></svg>
@@ -13,4 +37,4 @@
     {{- params.html | safe if params.html else params.text -}}
   </div>
 
-</div>
+</div>