onExecuteCommand  
  fun onExecuteCommand(connectFlags: <Error class: unknown class> = ConnectFlags(0u), handler: (command: String) -> Boolean): <Error class: unknown class>(source)
The signal is emitted when a command should be executed. This might be something like :wq or :e <path>.
If the application chooses to implement this, it should return true from this signal to indicate the command has been handled.
Since
5.4
Parameters
connectFlags 
a combination of ConnectFlags
handler
the Callback to connect. Params: command the command to execute. Returns true if handled; otherwise false.