Fsnotes: Improve default line spacing and UX of line spacing preferences

[sloria]

Describe your feature request

In priority order:

1. The default line spacing (0) is too cramped to be very readable.
2. A slider (screenshot below) isn't an intuitive control for line spacing. A menu with "1", "1.5", "2" etc. would be easier to use and would allow me to more easily match my configurations across machines.
3. I expected to be able to configure the line spacing in the "Layout / Font" section of the Preferences. It wasn't until I found https://github.com/glushchenko/fsnotes/issues/262 that I found that the settings are in "Editor / Line Spacing".

Additional context
macOS

[sloria]

Re: 2, Bear also uses a slider for line spacing:

This still seems like an odd choice, but maybe it's fine to follow Bear's lead for now.

Re: 3, moving the "Note Font" (and possibly rename to just "Font") setting to the "Editor" tab would address the issue. Font, line spacing, and line width settings should be colocated.

[sloria]

It would also be good to have the "Reset to defaults" button, like in the Bear screenshot above. As a user, I expect a "reset" button when the controls are sliders.

[brianwood2783]

I agree. I think the slider can be maintained, but it could have "notches" like regular menus on macOS, for example when setting the trackpad sensibility:

I guess 7 or 8 notches would be sufficient (as in the scrolling speed). Another related issue is that as of 4.3.3, the note titles aren't perfectly centralized height-wise... could be because of the slider.