Add <br clear="both"> to fix anchor scroll position on Firefox

On desktop versions of Mozilla Firefox browser, clicking on
"Social Fabric" (English) or "Tissu social" (French):

- https://opendrr.github.io/national-human-settlement/en/index.html#nhsl_social_fabric_indicators-a
- https://opendrr.github.io/national-human-settlement/fr/#nhsl_social_fabric_indicators-a

would jumped to the wrong position, near the Data Resources heading of
the previous Physical Exposure section.  Apparently, Firefox’s Gecko
handles the layout after uncleared floating images differently than
Chrome’s Blink engine.

See also https://stackoverflow.com/questions/4673671/floating-elements-br-clear-both-in-a-better-css-way

docs/_pages/en/index.md

@@ -103,6 +103,8 @@ breadcrumbs:
     {% include nhsl-resources.html lang = page.lang layer = layer %}
   </div>
 
+  <br clear="both">
+
 {% endfor %}
 
 {% assign var_length = variables.size | minus: 3 %}

docs/_pages/fr/index.md

@@ -103,6 +103,8 @@ breadcrumbs:
     {% include nhsl-resources.html lang = page.lang layer = layer %}
   </div>
 
+  <br clear="both">
+
 {% endfor %}
 
 {% assign var_length = variables.size | minus: 3 %}