docs: add java comment conventions to README.md

Author: tom-weelborg

README.md

@@ -122,4 +122,7 @@ The following are lists of conventions that either *should* be followed or *must
   - May be added to:
     - `public static` constants
     - other `private` members
-  - Should explain **what** the code does and maybe **why**, but never **how**
+  - Should explain **what** the code does and maybe **why**, but never **how**
+- Comments:
+  - Should be avoided except for Javadoc
+  - Necessary information regarding behavior should be added as Javadoc instead (e.g. `@apiNote`, `@implNote`, `@implSpec`)