Update README.md

Added syntax description for puzzles, as per issue #95 on master repo.

README.md

@@ -55,6 +55,16 @@ pdd --exclude=src/**/* # exclude all files in src/
 Every puzzle has to be formatted like this (pay attention
 to the leading space in every consecutive line):
 
+```java
+/**
+ * @todo [puzzle marker]</[role]> <[description]>
+ */
+[related code]
+```
+\[\] - Replace with apropriate data (see text enclosed in brackets)  
+<>   - Omitable (enclosed data can be left out) 
+
+Example:
 ```java
 /**
  * @todo #234:15m/DEV This is something to do later