reword docs for @ prefix
@@ -372,7 +372,7 @@ Defaults to \"format\" if the NO_COLOR env is set and to \"none\" if stdout is n
/// header;
/// Add a header with an empty value.
///
- /// "@" postfix can be added to "=",":=","==" and ":" to read the value from a file e.g. "x-api-key:@api-key.txt".
+ /// An `@` prefix can be used to read a value from a file. For example: `x-api-key:@api-key.txt`.
///
/// A backslash can be used to escape special characters, e.g. "weird\:key=value".
///
