Add documentation for Preconditions, Aliases, Command Structure

Resolves #223

docs/guides/samples/require_owner.cs

@@ -0,0 +1,16 @@
+// Defining the Precondition
+
+// Specify that this precondition can target a Class (Module/Group) or Method (Command)
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+// Inherit from PreconditionAttribute
+public class RequireOwnerAttribute : PreconditionAttribute
+{
+    public readonly ulong OwnerId = 66078337084162048;
+
+    // Override the CheckPermissions method
+    public override Task<PreconditionResult> CheckPermissions(IMessage context, Command executingCommand, object moduleInstance)
+    {
+        // If the author of the message is '66078337084162048', return success; otherwise fail. 
+        return Task.FromResult(context.Author.Id == OwnerId ? PreconditionResult.FromSuccess() : PreconditionResult.FromError("You must be the owner of the bot."));
+    }
+}