modify website to collect citizen scientists emails through a sign-in mechanism

[aaarendt]

From our team call 3/18:

• it's been very difficult to track CS individuals and their contributions
• some other CS projects have people sign up and a database of users is built
• can we have a button on the website to give people the option of signing up?

[aaarendt]

• @jonahjoughin will explore WordPress plugins to see what is possible