use http2_push instead of http2_push_preload

This avoids needing to conditionally add nopush to each preloaded
resource in the Link header. There's also no support for pushing
JavaScript modules via http2_push_preload since nginx doesn't have
support for rel=modulepreload.

process-static

@@ -41,7 +41,7 @@ for file in static-tmp/**/*.css static-tmp/js/*.js static-tmp/mask-icon.svg; do
     replace+=";s@{{path|/${file#*/}}}@/${dest#*/}@g"
 done
 
-sed -i "$replace" static-tmp/**/*.html nginx-tmp/nginx.conf
+sed -i "$replace" static-tmp/**/*.html nginx-tmp/nginx.conf nginx-tmp/snippets/preload.conf
 
 gixy nginx-tmp/nginx.conf