This adds a new `useRememberedState()` React hook that effectively allows us to have user interface elements that "remember" their most recent value, even if the UI itself was unmounted at some point. (It only works for the lifetime of the page, however, so it doesn't remember values across page reloads; this is intentional, as I didn't want to have to worry about serialization or schema migration.)
The hook is now used in the randomizer widget and for some of the creature page widgets, to ensure that their settings are preserved more often than not.
This replaces the "randomize colors" and "randomize" buttons on the creature and mandala pages with a single randomizer widget that allows the user to choose whether they want to randomize the colors, symbols, or both.
By default, both colors and symbols are randomized.
Note that this is really only a temporary solution, though: ideally we'll want to provide a more powerful UI that allows users to mark _any_ parameter for randomization, e.g. via "pinning" values or somesuch.