Fix assets loading when WEB_DOMAIN ≠ LOCAL_DOMAIN (#6319)

Since 872a0d5b, assets URL are absolute and
not relative. Unfortunately, the domain used to build such URLs is the wrong
one: LOCAL_DOMAIN, and not WEB_DOMAIN, where the assets are stored.

config/webpack/configuration.js

@@ -27,7 +27,7 @@ function formatPublicPath(host = '', path = '') {
 
 const output = {
   path: resolve('public', settings.public_output_path),
-  publicPath: formatPublicPath(env.ASSET_HOST || env.LOCAL_DOMAIN, settings.public_output_path),
+  publicPath: formatPublicPath(env.ASSET_HOST || env.WEB_DOMAIN || env.LOCAL_DOMAIN, settings.public_output_path),
 };
 
 module.exports = {