Full support for embed arrays in .greet/.bye, .say and other commands which use embeds

- Website to create them is live at eb2.nadeko.bot (it will soon be replacing eb.nadeko.bot)
- Embed arrays don't have a plainText property (it's renamed to 'content')
- Embed arrays use color hex values instead of an integer
- Old embed format will still work
- There shouldn't be any breaking changes

src/NadekoBot/Modules/Utility/Patreon/PatreonRewardsService.cs

@@ -84,13 +84,12 @@ public class PatreonRewardsService : INService, IReadyExecutor
         try
         {
             using var http = _httpFactory.CreateClient();
-            using var content = new StringContent(string.Empty);
             using var res = await http.PostAsync("https://www.patreon.com/api/oauth2/token"
                                            + "?grant_type=refresh_token"
                                            + $"&refresh_token={creds.Patreon.RefreshToken}"
                                            + $"&client_id={creds.Patreon.ClientId}"
                                            + $"&client_secret={creds.Patreon.ClientSecret}",
-                content);
+                null);
 
             res.EnsureSuccessStatusCode();
 
@@ -149,7 +148,7 @@ public class PatreonRewardsService : INService, IReadyExecutor
             if (!success)
                 return;
         }
-
+        
         LastUpdate = DateTime.UtcNow;
         try
         {