add shortcut that opens a comment thread for most recent message in a channel (#6549)

app/command_shortcuts.go

@@ -37,7 +37,7 @@ func (me *ShortcutsProvider) GetCommand(T goi18n.TranslateFunc) *model.Command {
 }
 
 func (me *ShortcutsProvider) DoCommand(args *model.CommandArgs, message string) *model.CommandResponse {
-	shortcutIds := [28]string{
+	shortcutIds := [29]string{
 		"api.command_shortcuts.header",
 		// Nav shortcuts
 		"api.command_shortcuts.nav.header",
@@ -58,6 +58,7 @@ func (me *ShortcutsProvider) DoCommand(args *model.CommandArgs, message string)
 		"api.command_shortcuts.msgs.reprint_prev",
 		"api.command_shortcuts.msgs.reprint_next",
 		"api.command_shortcuts.msgs.edit",
+		"api.command_shortcuts.msgs.reply",
 		"api.command_shortcuts.msgs.comp_username",
 		"api.command_shortcuts.msgs.comp_channel",
 		"api.command_shortcuts.msgs.comp_emoji",