Fix: Newline on single comments, and span of escaped characters

[lemon-gith]

Just what it says, I've corrected for both of these behaviours and added these new rules to the README.

Please do check and verify that the references are correct, if you have an 'ideal' flex file.

And, also feel free to add a comment to merge this later, in April, to avoid conflicts with students currently doing Lab 1.

[Fiwo735]

I think the updated spec makes more sense, I've found the current one not obvious to understand at first.

I'd say it would be good to merge it a few days after Lab 1 deadline (Fri 30 Jan 2026 at 15:00) in case students have any extensions, so let's say, within a week from now? What do you say @johnwickerson? The automated testing would need to be updated accordingly.

Just a small note when merging later, we should remove "For 267 cohort" from the changelog.

[johnwickerson]

Nice, thanks Pierce! I'll leave this hanging for a while to make sure everybody is finished with the lab, but yes, I agree that this would be good to fix for next year. I'll have to think about how to update my reference implementation to match, haha!