decrease stress of sign up exericse

### How could the content be improved?

scheduling a checkout step in 5 minutes can be hard because etherpads are long lists that can overwhelm, sometimes people have a complicated calendar and may not be in a good position to commit to something during the training.

Add options to:
- practice logging into AMY
- create a gh account to be able to contribute (issues count!) to lessons
- set a reminder to schedule things (if picking/scheduling is hard)

### Which part of the content does your suggestion apply to?

https://github.com/carpentries/instructor-training/blob/main/episodes/14-checkout.md?plain=1#L52-L67

Read episodes/14-checkout.md at lines 52-67 and compare the current checkout exercise with the requested alternatives. Update that section so learners have options for practicing AMY login, creating a GitHub account, or setting a reminder when scheduling is difficult; done means the revised guidance addresses these three options without requiring a five-minute commitment.

Written by the indexing model from the issue text.