Improve lookahead documentation
Given that a colleague also was not able to spot my mistake on its own I know three people which missed the this issue.
It might be obvious for those with a better understanding so please feel free to reject (or reword) this proposal :)
@@ -18,6 +18,9 @@ use std::cell::RefCell;
/// [`ParseStream::peek`]: crate::parse::ParseBuffer::peek
/// [`ParseStream::lookahead1`]: crate::parse::ParseBuffer::lookahead1
///
+/// Please be aware that advancing the source stream with parse() will not advance
+/// the lookahead object.
+///
/// # Example
///
/// ```
