A menu entry representing an action, e.g. "New File".
In addition to the mandatory command property, an alternative command can be defined. It will be shown and invoked when pressing Alt while opening a menu.
The command to execute.
Icon class(es). If not specified the icon class associated with the specified command
command.iconClass) will be used if it exists.
A specific label for this action. If not specified the command label or command id will be used.
Menu entries are sorted in ascending order based on their
order strings. If omitted the determined
label will be used instead.
Optional expression which will be evaluated by the ContextKeyService to determine visibility
of the action, e.g.
resourceLangId == markdown.