Add option to use OpenSSL if available in CMake configuration

.github/workflows/test.yaml

@@ -161,6 +161,7 @@ jobs:
         -DCMAKE_TOOLCHAIN_FILE=${{ env.VCPKG_ROOT }}/scripts/buildsystems/vcpkg.cmake
         -DHTTPLIB_TEST=ON
         -DHTTPLIB_COMPILE=${{ matrix.config.compiled && 'ON' || 'OFF' }}
+        -DHTTPLIB_USE_OPENSSL_IF_AVAILABLE=${{ matrix.config.with_ssl && 'ON' || 'OFF' }}
         -DHTTPLIB_REQUIRE_ZLIB=ON
         -DHTTPLIB_REQUIRE_BROTLI=ON
         -DHTTPLIB_REQUIRE_ZSTD=ON