feat: add books collection

src/content/books/a-test-book.md

@@ -0,0 +1,7 @@
+---
+title: Here is my test book
+---
+
+# A test book
+
+Here we go!!

src/content/books/books.json

@@ -0,0 +1,5 @@
+{
+  "layout": "base",
+  "tags": "books",
+  "permalink": "books/{{ page.fileSlug }}/index.html"
+}

src/content/pages/books.md

@@ -0,0 +1,10 @@
+---
+permalink: /books/index.html
+layout: "base"
+---
+
+# Books page
+
+{% for book in collections.books %}
+{{ book.data.title }}
+{% endfor %}