add missing $ on docs

Co-Authored-By: Liege72 <65319395+Liege72@users.noreply.github.com>

docs/guides/interactions_framework/post_execution.md

@@ -48,7 +48,7 @@ async Task SlashCommandExecuted (SlashCommandInfo arg1, Discord.IInteractionCont
                         await arg2.Interaction.RespondAsync("Invalid number or arguments");
                         break;
                     case InteractionCommandError.Exception:
-                        await arg2.Interaction.RespondAsync("Command exception:{arg3.ErrorReason}");
+                        await arg2.Interaction.RespondAsync($"Command exception:{arg3.ErrorReason}");
                         break;
                     case InteractionCommandError.Unsuccessful:
                         await arg2.Interaction.RespondAsync("Command could not be executed");