Chapter 2 should explain that `read_line` appends to `String`.

[nothingnesses]

I recently ran into an issue because I wrongly assumed that read_line overwrites the contents of a String instead of appending to it. I think a factor in this was that the explanation for the behaviour of read_line in Chapter 2 was a bit ambiguous. It turns out, I wasn't alone either, as someone else did something similar.

To prevent confusion in the future, I think it would be better if this sentence is changed to something like:

The job of `read_line` is to take whatever the user types into standard input
and append that into a string, so it takes that string as an argument.

Or even:

The job of `read_line` is to take whatever the user types into standard input
and append that into a string (without overwriting its contents), so it takes
that string as an argument.

[femtoeu]

Has that been changed? Because now, it overwrites the string.