Add project files.

Beam.Temporary.Cli/StringExtensions.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Beam.Temporary.Cli {
+    public static class StringExtensions {
+        public static string Aggregate(this IEnumerable<string> str, string separator) {
+            if (!str.Any())
+                return string.Empty;
+            return str.Aggregate((x, y) => $"{x}{separator}{y}");
+        }
+    }
+}