[MERGED PR] Add an alternative Saltpetre recipe

[ohjoy]

not against buffing saltpeter production to pre p-nerf levels

but the time gate seems entirely mitigatable by just reacting in more than one container 😅

My first draft was imagining if reaction rate could be influenced by amount of compost, e.g. if the reaction always took 5 seconds, but I don't know if that's possible, and I'm concerned about miasma bombing by mixing the chems and then unleashing 250u miasma smoke, so I decided against it.

Anyway, I'm aware the time gate is mitigable, but that needs more containers, makes the player spend time filling them, and increases the rate of miasma generation, so I think it's an interesting tradeoff for antags instead of a trivial obstacle, if only marginally so.