Feature: Zoom font size with cmd+ and cmd-

[trevor-coleman]

Adds several options to the View menu to allow the user to:

• zoom in / out,
• reset zoom
• toggle fullscreen

The state will be persisted between sessions.

We did this by adding the roles to the view.submenu array in buildViewMenu

// apps/reactotron-app/src/main/menu.ts

viewMenu.submenu.push({
       // ...
    }, {
        role:'separator'
    }, {
        role: 'togglefullscreen'
    }, {
        role: 'resetZoom'
    },{
        role: 'zoomIn',
    }, {
        role: 'zoomOut',
    },  {
        role: 'separator'
    },);

[trevor-coleman]

With contributions from @twerth and @derekgreenberg