Add fluid ingredient into the ingredient section of docs

[TelepathicGrunt]

The PR: https://github.com/neoforged/NeoForge/pull/789

This need updating https://docs.neoforged.net/docs/resources/server/recipes/ingredients

Will be linked into this gist https://gist.github.com/TelepathicGrunt/4de77c67adb661c9380e594d20b6a58b