Add monster_extra files to Bazel cc_test section (#5321)

- add monster_extra.fbs
- add monsterdata_extra.json

BUILD

diff --git a/BUILD b/BUILD
index 567a133..a7a79b3 100644
--- a/BUILD
+++ b/BUILD
@@ -161,6 +161,8 @@
         ":tests/unicode_test.json",
         ":tests/union_vector/union_vector.fbs",
         ":tests/union_vector/union_vector.json",
+        ":tests/monster_extra.fbs",
+        ":tests/monsterdata_extra.json",
     ],
     includes = ["include/"],
     deps = [