Added docs for usage with templates

doc/03-Templates.md

@@ -18,5 +18,20 @@ In the latter, you might want to blacklist some tags and only process text in
 certain places, this can easily be accomplished with:
 
 ```clojure
-
+(defn process-template [mdast template-vals]
+  (clojure.walk/prewalk
+   (fn [item]
+     (if (cybermonday.utils/hiccup? item)
+       (let [[tag attrs & body] item]
+         (if (not= tag :code)
+           (cybermonday.utils/make-hiccup-node
+            tag
+            attrs
+            (map #(if (string? %)
+                    (pogonos.core/render-string % template-vals)
+                    %)
+                 body))
+           item))
+       item))
+   mdast))
 ```