ci.yml: enable openssl-async to test this feature

Author: chobits

.github/workflows/ci.yml

@@ -46,6 +46,7 @@ jobs:
          ./configure \
             --with-ld-opt="-Wl,-rpath,/usr/local/lib" \
             --with-ipv6 \
+            --with-openssl-async \
             --with-http_ssl_module \
             --with-http_v2_module \
             --with-http_addition_module \