Sedrila

- ...

- increase inter-version compatibility between authors and recipients (students/instructors)
- `author`: documentation describes how to get an English translation using ChatGPT.

- `author`: FIX: generated `course.json` now includes the required attribute `altdir`

- `author`: introduce `itreedir` and `[TREEREF]` for stand-alone instructor support files

- `author`: allow task names containing a dot

- `author`: table of contents for glossary now is chapters-only
- `author`: warn about unterminated INSTRUCTOR blocks (that would show up in student version)
- `author`: warn about macro calls with empty arg1
- `student --submission`: FIX: solve terminal-size-dependent crash
- `student`: FIX: work around surprising limitation in `rich` library to produce the work table again