Scrollback should be included in default config .hyper.js

[corneliusroemer]

Is your feature request related to a problem? Please describe.
Current default scrollback is rather small (1000 lines). To make matters worse, while the value is configurable (via config.scrollback) this option is not included in the default config .hyper.js that one gets after installing hyper.

Describe the solution you'd like
Include scrollback in the default .hyper.js

Additional context
This has been raised before in a comment by @PButcher: #3038 (comment)

I'm making this an issue to make it more discoverable.