add error log when root element isn't found

[w3irdrobot]

closes #1231

[ealmloff]

It looks like we only enable the console feature of web-sys here if the hydrate feature is enabled. The workspace has that feature enabled, so I don't think the issue will show up in CI, but we need to add it to the list of web-sys features that are always enabled here

[ealmloff]

This will make a missing root id much easier to debug. Thank you!