Add instructions how to add new co-organizers

[cosimameyer]

Here's a section on co-organizers: add instructions on how to add them here as well ☺️

https://guide.rladies.org/organization/intro/co-organizers/

FYI: @MounaBelaid I believe you know best what's the procedure (and we can update it with the link to the new form once it's confirmed it's running)

[drmowinckels]

Duplicate of #18

[cosimameyer]

I’ll go ahead and close it since it’s a duplicate. I’ll be referenced in the other issue stream anyway.