feat(frontmatter): separate frontmatter & content

Added function to read a file and separate frontmatter from content.

resources/test.md

@@ -1,3 +1,6 @@
+---
+title: This is a test document
+---
 # Test document
 
 This is a test document that we should be able to convert to HTML.

src/main.lisp

@@ -2,4 +2,21 @@
   (:use :cl))
 (in-package :homestead)
 
-;; blah blah blah.
+(defun separate-content-and-frontmatter (file-path)
+  (with-open-file (stream file-path)
+    (let* ((line (read-line stream nil nil))
+            (in-frontmatter (string= line "---"))
+            frontmatter
+            content)
+      (setf frontmatter (with-output-to-string (s)
+                          (when in-frontmatter
+                            (loop while in-frontmatter do
+                              (setf line (read-line stream nil nil))
+                              (if (string= line "---")
+                                (setf in-frontmatter nil)
+                                (write-line line s))))))
+      (setf content (with-output-to-string (s)
+                      (loop with end-of-file = nil
+                        while (setf line (read-line stream nil end-of-file))
+                        do (write-line line s))))
+      (list frontmatter content))))