Also test with macOS 11

Author: MaxDesiatov

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     name: Build and Test
     strategy:
       matrix:
-        os: [macOS-10.15, Ubuntu-18.04]
+        os: [macos-10.15, macos-11, ubuntu-18.04]
         toolchain:
           - wasm-5.3.1-RELEASE
           - wasm-5.4.0-RELEASE