Force a linebreak so that the "External Article" button appears on its own line (#65)

[reviewed by @DanilaFe and design agreed upon by @e-kayrakli]

To me, this made article titles easier to parse while also making the
external article visual tag clearer.

### Before
<img width="1126" height="1900" alt="image"
src="https://github.com/user-attachments/assets/1ea9dcd6-dcfb-4ef9-a118-734c6a61e200"
/>

### After
<img width="1120" height="1872" alt="image"
src="https://github.com/user-attachments/assets/120baac7-9937-4923-a039-9c344c30706c"
/>

Author: bradcray

themes/chapel-theme/layouts/partials/post.html

@@ -7,7 +7,7 @@
         {{- if .Params.featured }}{{ partial "icon.html" "star" }}{{ end }}
         {{- " " -}}{{ partial "richtitle.html" . }}
         {{- if .Params.externalURL -}}
-        <span class="external-marker">
+        <br><span class="external-marker">
             External Article {{ partial "icon.html" "external-link" }}
         </span>
         {{- end -}}