Add linter-friendly WeightedRandom prototypes (#18729)

Content.Shared/Random/IWeightedRandom.cs

@@ -0,0 +1,13 @@
+using Robust.Shared.Prototypes;
+
+namespace Content.Shared.Random;
+
+/// <summary>
+/// IWeightedRandomPrototype implements a dictionary of strings to float weights
+/// to be used with <see cref="Helpers.SharedRandomExtensions.Pick(IWeightedRandomPrototype, Robust.Shared.Random.IRobustRandom)" />.
+/// </summary>
+public interface IWeightedRandomPrototype : IPrototype
+{
+    [ViewVariables]
+    public Dictionary<string, float> Weights { get; }
+}