Add UI element to change font size

[diniamo]

The title is self-explanatory, the default font size is way too big for small images.

[jacekpoz]

any suggestions on where the UI for that could be and what it could look like?

[diniamo]

Probably an input field with +- buttons on the bottom, next to the SML buttons. It would also be nice to preserve the value between Satty instances.

[gabm]

I agree.. but i don't have a 100% good idea on how to keep the interface lean with the increasing number of options/settings

[gabm]

there are some ideas in #42 and #49

[00-kat]

The SML buttons could be replaced with a
- A +
when the font tool is selected maybe. The A could be the current font size, instead of showing the number.

I was thinking of maybe sending a PR which replaces SML with - o + where o is the current pen size (after I figure out GTK), so if I ever do that this would fit in even more...

[diniamo]

Could work to be honest.