support semicolon inference

[soc]

Treat a newline as ; except when:

• we are inside ( or [
• the the token before or after the newline is an operator

https://pling.jondgoodwin.com/post/semicolon-inference/

[soc]

A not-up-to-date work-in-progress draft is in https://github.com/core-lang/core/pull/74.