Rewrite all concepts documentation

hello RC documentation

docs/guides/concepts/samples/events.cs

@@ -0,0 +1,31 @@
+using Discord;
+using Discord.WebSocket;
+
+public class Program
+{
+	private DiscordSocketClient _client;
+	static void Main(string[] args) => new Program().MainAsync().GetAwaiter().GetResult();
+	
+	public async Task MainAsync()
+	{
+		_client = new DiscordSocketClient();
+
+		await _client.LoginAsync(TokenType.Bot, "bot token");
+		await _client.StartAsync();
+
+		_client.MessageUpdated += MessageUpdated;
+		_client.Ready += () => 
+		{
+			Console.WriteLine("Bot is connected!");
+			return Task.CompletedTask;
+		}
+		
+		await Task.Delay(-1);
+	}
+
+	private async Task MessageUpdated(Cacheable<IMessage, ulong> before, SocketMessage after, ISocketMessageChannel channel)
+	{
+		var message = await before.GetOrDownloadAsync();
+		Console.WriteLine($"{message} -> {after}");
+	}
+}