Added new getting started guide

Thanks @MinnDevelopment for his awesome work on
the JDA guide that had no influence here at all.

docs/guides/samples/intro/client.cs

@@ -0,0 +1,16 @@
+// Program.cs
+using Discord.WebSocket;
+// ...
+public async Task MainAsync()
+{
+	var client = new DiscordSocketClient();
+
+	client.Log += Log;
+
+	string token = "abcdefg..."; // Remember to keep this private!
+	await client.LoginAsync(TokenType.Bot, token);
+	await client.StartAsync();
+
+	// Block this task until the program is closed.
+	await Task.Delay(-1);
+}