Add example posts with header tagline

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

@@ -0,0 +1,28 @@
+---
+title: "Layout: Header Image Overlay with Custom Tagline"
+tagline: "This is a custom tagline content which overrides the *default* page excerpt."
+header:
+  overlay_image: /assets/images/unsplash-image-1.jpg
+  caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
+categories:
+  - Layout
+  - Uncategorized
+tags:
+  - edge case
+  - image
+  - layout
+last_modified_at: 2020-01-07T13:05:25-05:00
+---
+
+This post should display a **header with an overlay image** and **custom tagline**, if the theme supports it.
+
+Non-square images can provide some unique styling issues.
+
+This post tests overlay header images with custom `page.tagline`.
+
+```yaml
+tagline: "This is a custom tagline content which overrides the default page excerpt."
+header:
+  overlay_image: /assets/images/unsplash-image-1.jpg
+  caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
+```

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

@@ -0,0 +1,28 @@
+---
+title: "Layout: Header Image Overlay with Custom Tagline"
+tagline: "This is a custom tagline content which overrides the *default* page excerpt."
+header:
+  overlay_image: /assets/images/unsplash-image-1.jpg
+  caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
+categories:
+  - Layout
+  - Uncategorized
+tags:
+  - edge case
+  - image
+  - layout
+last_modified_at: 2020-01-07T13:05:25-05:00
+---
+
+This post should display a **header with an overlay image** and **custom tagline**, if the theme supports it.
+
+Non-square images can provide some unique styling issues.
+
+This post tests overlay header images with custom `page.tagline`.
+
+```yaml
+tagline: "This is a custom tagline content which overrides the default page excerpt."
+header:
+  overlay_image: /assets/images/unsplash-image-1.jpg
+  caption: "Photo credit: [**Unsplash**](https://unsplash.com)"
+```