Rename "template" to "layout" to match Jekyll nomenclature

_posts/2012-03-15-layout-header-overlay-image.md

@@ -0,0 +1,20 @@
+---
+title: "Layout: Header Image Overlay"
+header:
+  overlay_image: unsplash-image-1.jpg
+  caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
+  cta_url: "https://unsplash.com"
+categories:
+  - Layout
+  - Uncategorized
+tags:
+  - edge case
+  - image
+  - layout
+---
+
+This post should display a **header with an overlay image**, if the theme supports it.
+
+Non-square images can provide some unique styling issues.
+
+This post tests overlay header images.