[font overview] Make side bar resizable

[ollimeier]

No description provided.

[ollimeier]

@justvanrossum
Currently the resize logic of the editor view is stored in Sidebar -> initResizeGutter which will be added via:

  initSidebars() {
    this.addSidebar(new Sidebar("left"));
    this.addSidebar(new Sidebar("right"));

I am wondering if we should be using the same logic for our new font overview, because we may potentially see also for example a right sidebar containing glyph information or if we should 'only' make the one left sidebar resizable?

[justvanrossum]

While the concept of tabbed sidebars does not make sense in the font overview (at with that specific visual design + behavior), I am fairly sure a right-hand sidebar is something we will need sooner or later.