This commit continues work laid out by ffec8163b0 for the admin config page for the /about page. The last commit set up the user interface, and this one sets up all the wiring needed to make the input fields and save buttons actually work.
Internal topic: t/128544.
This commit introduces the initial UI for the admin config area for the /about page. The UI isn't wired and doesn't do anything yet, but we're going to iterate on it in future commits.
Internal topic: t/128544.