Chore: formatting, fix types and missing dev deps

[thetarnav]

• add format script, (and prettier)
• add missing dev deps, (@types/babel__generator, @types/node, tslib)
• fix types in create-proxy
• adds { internal: true } option to created signals

[lxsmnsyc]

lgtm. I'd approve this now since I have to rework the HMR codegen