Terser leading/trailing syntax in scm

[AndreasArvidsson]

Fixes #2108

Checklist

• [-] I have added tests
• [-] I have updated the docs and cheatsheet
• [-] I have not broken the cheatsheet

[pokey]

Wow yeah way more readable

On an extremely minor note, I have very mixed feelings about the convention you're starting to introduce of functions that accept undefined on one of their params and return undefined in that case. Feels like it's conflating concerns. I tried rewriting it to use null-ish chaining and I think it worked well (f5dc428). I don't feel super strongly, so if you want to roll back that's fine, was just curious if it could be done with nullish chaining. If you do roll back, let's come up with a better name for that function. I think the convention could work if we come up with a solid naming convention to go along with it