Add docs about citing and referring to the combined platform

[mekline]

Modify from this Slack announcement:

Because we've recently done a platform merger, people have been asking how to refer the project when writing about it. I will add this to the documentation as well, but as a summary, if you are writing a grant that will collect data on the platform, please do something like the following:

• The first time you refer to the platform, please include something like the following: "...In 2023, these platforms (Lookit and Children Helping Science) merged to form a single platform running on the existing Lookit architecture. The platform is now advertised to participating families as Children Helping Science (CHS)."
• In subsequent text, please refer to the platform that you will run/advertise studies on as Children Helping Science or CHS.
• You can continue to use Lookit to refer to previous studies that were done on the platform (or CHS to refer to studies done on that website!)
• When talking about technical details of implementing an internal study, you can also refer to the "Lookit experiment builder."

Please don't stress about it if you've recently submitted something that doesn't do this...academia moves slowly and it'll be a while of ambiguity, but if everyone moves in a more-or-less consistent direction, there will be less chance for people to get confused or lose track of what the platform is.

(This also goes for writing papers - if you completed data collection prior to 2023, we will really appreciate a note in your methods section along these same lines, e.g. "We collected this on Lookit, which is now called CHS", if you are working now and planning to write something, "We collected this on Children Helping Science, a platform for remote data collection created by the 2023 merger of Lookit (Scott & Schulz, 2017) and Children Helping Science (Sheskin et al. 2020)")

(Hopefully in not too long we'll have a citation for the merged platform, which has lots of features that aren't referenced in either of those!)