Update issue text for making the draft schedule

[sjspielman]

We should update guidance in this issue template - https://github.com/AlexsLemonade/training-specific-template/blob/main/setup-issue-templates/draft-schedule.md

Slides and completed notebooks are not likely to exist yet when the draft schedule is written. We should provide better guidance on what temporary relative links to use (for example, use fake # anchor links so at least nothing will 404) for files that haven't been created yet.