Use readonly by default unless you save the file

[PerfectlyFineCode]

Hi!

I've been using ImHex to read the save file of my program, however that also means ImHex locks the file so my own program can't access the file.

It would be a significantly better experience if it could open the file as readonly and you edit the file in-memory and when you save it, it will open the same file (or upgrade it) with write access.

That way there should be no issues with readonly / write access, but it will dynamically switch between them.