Preview window fonts are super tiny on HDPI screens

[SimonEast]

I'm using CuteMarkEd on Windows and have a high density (HDPI) laptop screen and the preview window text is super tiny.

There's actually several bugs associated with this:

1. The zoom level is not saved between launches of CuteMarkEd, so it has to be reapplied each time. This is probably the easiest to fix and would (mostly) resolve the issue.

2. It would be great if the HTML renderer (or CuteMarkEd itself) detected the DPI of the screen and adjusted accordingly. Note that users may be using multiple monitors of varying DPI's so this may need to be adjusted when moving between monitors.

3. The keyboard shortcut for the zoom level does not work (at least not on my machine) so I have to use the right-click menu which is tedious to zoom in about 10 times.

4. The text size settings under Options > HTML Preview don't appear to do anything.

[SimonEast]

Actually a correction: the keyboard shortcuts for zoom do work, but it's confusing, since it's labelled as CTRL++ but actually requires the shift key, so it's more like CTRL+SHIFT+=.