Document process to be added as a Bluesky Reviewer

As the number of people contributing to dodal is increasing, the ratio of PR's to reviewers is starting to grow and have an impact on the backlog of when something can be reviewed within a timely manner. There needs to be a system in place documenting the procedure on how someone can be added to the Bluesky Reviewers list so that it can keep pace.

Code quality must be maintained, however there needs to be a balance as a new reviewer will only get better with experience which they can only get by doing reviews.

Maybe a check list would be good for new reviewers, and if the change is larger than X size a more experienced member could help double check it.