chore: adding failing grind test

tests/lean/grind/hashmap_list.lean

@@ -0,0 +1,18 @@
+import Std.Data.HashMap
+
+reset_grind_attrs%
+
+open Std
+
+attribute [grind →] List.length_pos_of_mem
+attribute [grind] HashMap.size_insert
+
+-- Fails with issue:
+-- [issue] type error constructing proof for List.length_pos_of_mem
+--     when assigning metavariable ?l with
+--       m.insert 1 2
+--     has type
+--       HashMap Nat Nat : Type
+--     but is expected to have type
+--       List Nat : Type
+example (m : HashMap Nat Nat) : ((m.insert 1 2).insert 3 4).size ≤ m.size := by grind