Change upload path month to be 1-indexed instead of 0-indexed

Jan=1 and Dec=12, not Jan=0 and Dec=11. Because that's just too
confusing ;P

functions.js

@@ -104,9 +104,9 @@ const pushToGhost = async (postSlug) => {
   // Decide WebDAV upload path
   current_date = new Date()
 
-  var uploadPath = path.join(
+  const uploadPath = path.join(
     current_date.getUTCFullYear().toString(),
-    current_date.getUTCMonth().toString(),
+    (current_date.getUTCMonth() + 1).toString(),
     postSlug
   )