Add a menu item allowing a user to change their sparkle auto update settings

[AliSoftware]

In particular we need the user to be able to:

• Change the default font size (and even the font?) of the Podfile Editor window
• Choose if they want automatic Sparkle updates or not (after the Sparkle dialog on 2nd launch there is no way to change that setting from the app for now)

Sure for now we don't have a lot of preferences so that might also be dedicated Menu items, but we'll surely add more stuff in the future so this is always useful to have a dedicated Preferences window for all that.

[alloy]

Ideally we'd have no preferences imo.

For instance, the font size issue can simply be handled by adding cmd-+/- support and save those changes to the user defaults.

The Sparkle one is tougher, that might need to be a menu item indeed.

[orta]

Font size is addressed. Thanks @wrutkowski

We definitely shouldn't have a prefs window for this, so I've renamed the title of the issue.