adds feature(alloc_error_handler) to main

src/main.rs

@@ -11,6 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+#![feature(alloc_error_handler)]
 
 #![cfg_attr(not(feature = "std"), no_std)]