Test enums.

Author: robrix

languages/tree-sitter-stack-graphs-java/test/decl/enum.java

@@ -0,0 +1,11 @@
+enum A {
+  X, Y, Z
+}
+
+class B {
+    A f() {
+  //^ defined: 1
+    f(X);
+    //^ defined: 2
+  }
+}