Modify template to add if-else structure

hypha/apply/stream_forms/templates/stream_forms/heading_field.html

-<{{ value.size }} id="{{ value.heading_text|slugify }}">{{ value.heading_text }}
-    <a href="#{{ value.heading_text|slugify }}">
-        <svg class="icon icon--anchor-link">
-            <use xlink:href="#anchor-link"></use>
-        </svg>
-    </a>
-</{{ value.size }}>
+{% if self.size == 'h2' %}
+        <h2 id="{{ value.heading_text|slugify }}">{{ value.heading_text }}
+            <a href="#{{ value.heading_text|slugify }}">
+                <svg class="icon icon--anchor-link">
+                    <use xlink:href="#anchor-link"></use>
+                </svg>
+            </a>
+        </h2>
+
+    {% elif self.size == 'h3' %}
+        <h3 id="{{ value.heading_text|slugify }}">{{ value.heading_text }}
+            <a href="#{{ value.heading_text|slugify }}">
+                <svg class="icon icon--anchor-link">
+                    <use xlink:href="#anchor-link"></use>
+                </svg>
+            </a>
+        </h3>
+
+    {% elif self.size == 'h4' %}
+        <h4 id="{{ value.heading_text|slugify }}">{{ value.heading_text }}
+            <a href="#{{ value.heading_text|slugify }}">
+                <svg class="icon icon--anchor-link">
+                    <use xlink:href="#anchor-link"></use>
+                </svg>
+            </a>
+        </h4>
+{% endif %}