Output error messages into a document in development mode

[v1rtl]

Instead of opening console it is better to output errors on the screen for a more convinient development.

Parcel and CRA already do this

[osdevisnot]

This seems a very good idea. I will try to get around this when I get a chance. For starters, we use servor from @lukejacksonn as zero dependency hot reloading server to power klap, just in case if someone wants to give it a try.