Document that javadoc shouldn't appear between annotations and the documented element

PiperOrigin-RevId: 591893421

Author: cushon

docs/bugpattern/javadoc/NotJavadoc.md

@@ -14,6 +14,23 @@ Suggested solutions:
 *   If the comment is intended to be an implementation comment, use a
     single-line `//` or a multi-line `/*` comment instead.
 
+> NOTE: Javadoc must appear before any annotations, or the compiler will fail to
+> recognise it as Javadoc. That is, prefer this:
+>
+> ```java
+> /** Might return a frobnicator. */
+> @Nullable
+> Frobnicator getFrobnicator();
+> ```
+>
+> instead of this:
+>
+> ```java
+> @Nullable
+> /** Might return a frobnicator. */
+> Frobnicator getFrobnicator();
+> ```
+
 ## Suppression
 
 Suppress by applying `@SuppressWarnings("NotJavadoc")` to the enclosing element.