fix(theme): styles

renamed featured header image class on article pages so that they're (somewhat) more distinct from article preview images on list pages

blog/themes/mineral/layouts/_default/single.html

@@ -6,7 +6,7 @@
     </div>
 
     {{if isset .Params "image" }}
-        <img src="{{ index .Params "image" }}" alt="{{ .Title }}" class="preview">
+        <img src="{{ index .Params "image" }}" alt="{{ .Title }}" class="heading">
     {{ end }}
 
     <article class="row content" style="margin-top: 2em">

blog/themes/mineral/static/css/mineral.css

@@ -55,6 +55,6 @@ article p img {
     hyphens: auto;
 }
 
-img.preview {
+img.preview, img.heading {
     width: 100%;
 }