Move the Coolants page to the Essentials section

[diogovalada]

Could it make sense to move the coolants page (https://whatisnuclear.com/coolants.html) to the Essentials section?

Right now it is on the "Reactors" section, which maybe is not ideal. Plus, the moderators article is already in the essentials section, and I guess it would make sense to move coolants there as well.

After all, fuel, coolant, and moderator (well...), are the three essentials in nuclear reactors.