[Feature Request]: add option to hide panel on every opened file

[PetbkA]

1. I've opened my notes that's 100 KBytes file;
2. I've enabled panel - everything's OK;
3. Forgot to disable panel and opened 300 MByte file - NOK, NP++ hangs 'cause panel tries to render it in Markdown.

It would be nice if panel would hide on every opened file. Another way is add an ability to "cancel" rendering on "Show panel" hotkey