(lab 5) feat: add Number Operations example

lab 5/NumberOperations/NumberOperations.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+
+</Project>

lab 5/NumberOperations/Program.fs

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+// For more information see https://aka.ms/fsharp-console-apps
+printfn "Hello from F#"
+
+let rec sumDigits n =
+    if n < 10 then n
+    else (n % 10) + sumDigits (n / 10)
+
+[<EntryPoint>]
+let main argv =
+    System.Console.WriteLine("Введите число:")
+    let number = System.Console.ReadLine() |> int
+    
+    let result = sumDigits number
+    System.Console.WriteLine($"Сумма цифр числа {number} равна {result}")
+    
+    0