Add margin-bottom to standalone blog post images (#199)

* Initial plan

* Add margin-bottom to blog post images for spacing below hero images

Co-authored-by: grst <7051479+grst@users.noreply.github.com>
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* Scope margin-bottom to direct child images only, preserving figure caption spacing

Co-authored-by: grst <7051479+grst@users.noreply.github.com>
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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: grst <7051479+grst@users.noreply.github.com>

Author: Copilot

assets/main.scss

@@ -940,6 +940,10 @@ body {
             margin: 3rem 0;
             font-size: 1.1rem;
             text-wrap: pretty;
+            > img,
+            > p > img {
+                margin-bottom: 1.5rem;
+            }
             span.backticked {
                 font-size: 1.2rem;
                 line-height: 1.1rem;