api: Add go files

I know this is a huge commit, but I can't be bothered to check
this in part by part.

api/markdown_html.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"gopkg.in/russross/blackfriday.v1"
+)
+
+func markdownToHtml(markdown string) string {
+	unsafe := blackfriday.Markdown([]byte(markdown), renderer, extensions)
+	return string(policy.SanitizeBytes(unsafe))
+}