`console.warn` only shown when clicking "output" tab

[titoBouzout]

Ryan noted that markup validation wasn't shown as an error https://discord.com/channels/722131463138705510/817960620736380928/1428818452168048671

We use console.warn and do not throw for that particular case, but even then the warning is only shown when clicking the "output" tab. https://playground.solidjs.com/anonymous/484af2b6-3962-4b27-b978-2bd01ad7d660

Could be also considered to show console.warn as errors(message below code), not sure if that were a thing before