Small readability issues on overview page

[jfhector]

Thanks @lubes72 for this feedback:

• 'pre-recorded' (rather than 'prerecorded')
• don't contract negatives
  • e.g. 'do not' (rather than 'don't')
• don't use 'e.g.' or 'i.e.'
  • use 'for example' or 'like'
• don't say 'do not require' as that's not clear
  • It might be better to say something like 'do not make [something] required'