Add WaterCluster to docs
Under both `Clusters and simple fluids` and `Water boxes`
@@ -59,6 +59,7 @@ Clusters and simple fluids
TolueneImplicitGBn
TolueneImplicitGBn2
MethanolBox
+ WaterCluster
Solids
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@@ -91,6 +92,7 @@ Water boxes
GiantFlexibleDischargedWaterBox
DischargedWaterBoxHsites
AlchemicalWaterBox
+ WaterCluster
Peptide and protein systems
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