Add support of ignore tag for json.marshal

tests/core/encoding/json/test_core_json.odin

@@ -368,4 +368,25 @@ utf8_string_of_multibyte_characters :: proc(t: ^testing.T) {
 	val, err := json.parse_string(`"🐛✅"`)
 	defer json.destroy_value(val)
 	testing.expectf(t, err == nil, "Expected `json.parse` to return nil, got %v", err)
+}
+
+@test
+struct_with_ignore_tags :: proc(t: ^testing.T) {
+	My_Struct :: struct {
+		a: string `json:"_,ignore"`,
+	}
+
+	my_struct := My_Struct{
+		a = "test",
+	}
+
+	my_struct_marshaled, marshal_err := json.marshal(my_struct)
+	defer delete(my_struct_marshaled)
+
+	testing.expectf(t, marshal_err == nil, "Expected `json.marshal` to return nil error, got %v", marshal_err)
+
+	my_struct_json := transmute(string)my_struct_marshaled
+	expected_json := `{}`
+
+	testing.expectf(t, expected_json == my_struct_json, "Expected `json.marshal` to return %s, got %s", expected_json, my_struct_json)
 }