Grammar rules to make the epilogue declaration optional in the parser input

```diff
diff --git a/lib/lrama/grammar/stdlib.y b/lib/lrama/grammar/stdlib.y
index fc20e0a..b6196d9 100644
--- a/lib/lrama/grammar/stdlib.y
+++ b/lib/lrama/grammar/stdlib.y
@@ -116,7 +116,3 @@
  */
 %rule separated_list(separator, X): option(separated_nonempty_list(separator, X))
                                   ;
-
-%%
-
-%union{};
```

Author: ydah

lib/lrama/grammar/stdlib.y

@@ -116,7 +116,3 @@
  */
 %rule separated_list(separator, X): option(separated_nonempty_list(separator, X))
                                   ;
-
-%%
-
-%union{};