Fix Samples on Docs; Fix Links on Docs; add FAQ page to docs

docs/guides/samples/faq/avatar.cs

@@ -0,0 +1,5 @@
+public async Task ChangeAvatar()
+{
+    var fileStream = new FileStream("./newAvatar.png", FileMode.Open);
+    await (await _client.GetCurrentUserAsync()).ModifyAsync(x => x.Avatar = fileStream);
+}

docs/guides/samples/faq/send_message.cs

@@ -0,0 +1,7 @@
+public async Task SendMessageToChannel(ulong ChannelId)
+{
+    var channel = await _client.GetChannelAsync(ChannelId) as IMessageChannel;
+    await channel?.SendMessageAsync("aaaaaaaaahhh!!!")
+    /*           ^ This question mark is used to indicate that 'channel' may sometimes be null, and
+                    in cases that it is null, we will do nothing here. */ 
+}

docs/guides/samples/faq/status.cs

@@ -0,0 +1,8 @@
+public async Task ModifyStatus()
+{
+    await (await _client.GetCurrentUserAsync()).ModifyStatusAsync(x =>
+    {
+        x.Status = UserStatus.Idle;
+        x.Game = new Game("Type !help for help");
+    });
+}