fix compile error, and include example preview

[enghitalo]

Why did is not get by .github/workflows/v_apps_and_modules_compile_ci.yml? on V CI?

      - name: Build vlang/msgpack
        run: |
          echo "Install msgpack"
          v install msgpack
          echo "Build msgpack"
          v -shared ~/.vmodules/msgpack/
          echo "Run msgpack tests"
          v -stats test ~/.vmodules/msgpack/
          echo "MessagePack examples should compile"
          v should-compile-all ~/.vmodules/msgpack/examples