[DOC] Add changelog entry

Signed-off-by: Lydia Buntrock <[email protected]>

CHANGELOG.md

@@ -23,3 +23,13 @@ The following API changes should be documented as such:
 
 If possible, provide tooling that performs the changes, e.g. a shell-script.
 -->
+
+## API changes
+
+#### I/O
+
+To avoid using seqan3::io we changed the usage of the `seqan3::input_file_validator` from
+`seqan3::input_file_validator<seqan3::sequence_file_input<>> validator{}` to
+`seqan3::input_file_validator validator{seqan3::sequence_file_input<>::valid_formats}` and
+`seqan3::output_file_validator<seqan3::sequence_file_input<>> validator{}` to
+`seqan3::output_file_validator validator{output_file_open_options const mode, seqan3::sequence_file_input<>::valid_formats}`.