Add sample bots to the solution (#972)

* Add sample bots to the solution

* Fix missing attributes, show use of preconditions

samples/02_commands_framework/Program.cs

@@ -0,0 +1,60 @@
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Microsoft.Extensions.DependencyInjection;
+using Discord;
+using Discord.WebSocket;
+using Discord.Commands;
+using _02_commands_framework.Services;
+
+namespace _02_commands_framework
+{
+    // This is a minimal example of using Discord.Net's command
+    // framework - by no means does it show everything the framework
+    // is capable of.
+    //
+    // You can find samples of using the command framework:
+    // - Here, under the 02_commands_framework sample
+    // - https://github.com/foxbot/DiscordBotBase - a barebones bot template
+    // - https://github.com/foxbot/patek - a more feature-filled bot, utilizing more aspects of the library
+    class Program
+    {
+        static void Main(string[] args)
+            => new Program().MainAsync().GetAwaiter().GetResult();
+
+        public async Task MainAsync()
+        {
+            var services = ConfigureServices();
+
+            var client = services.GetRequiredService<DiscordSocketClient>();
+
+            client.Log += LogAsync;
+            services.GetRequiredService<CommandService>().Log += LogAsync;
+
+            await client.LoginAsync(TokenType.Bot, Environment.GetEnvironmentVariable("token"));
+            await client.StartAsync();
+
+            await services.GetRequiredService<CommandHandlingService>().InitializeAsync();
+
+            await Task.Delay(-1);
+        }
+
+        private Task LogAsync(LogMessage log)
+        {
+            Console.WriteLine(log.ToString());
+
+            return Task.CompletedTask;
+        }
+
+        private IServiceProvider ConfigureServices()
+        {
+            return new ServiceCollection()
+                .AddSingleton<DiscordSocketClient>()
+                .AddSingleton<CommandService>()
+                .AddSingleton<CommandHandlingService>()
+                .AddSingleton<HttpClient>()
+                .AddSingleton<PictureService>()
+                .BuildServiceProvider();
+        }
+    }
+}