Editor docs needs updated with new system for finding reviewers

[AoifeHughes]

• https://github.com/openjournals/joss/blob/main/docs/editing.md
• This link to the dashboard is also not rendering as correct markdown

I can make a PR to fix this later today (unless anyone else is super keen)

[xuanxu]

Fixed in https://github.com/openjournals/joss/pull/1290