Feature: Add workspace switching by horizontally scrolling sidebar

[kristijanribaric]

This PR adds the ability to switch workspaces by horizontally scrolling the sidebar. A scroll cooldown and threshold are implemented to prevent accidental workspace changes. The _setupHoverDetection method is renamed to _setupSidebarHandlers as it now handles both hover and scroll events.

[mr-cheff]

Thanks!

[iskaa02]

wouldn't be better to make the switching animation a non-linear animation.
my idea would be rendering the next and previous workspaces, when switching animate the position (also animate background) by interpolating gesture/scroll, and when the animation is finished switch the workspace, this would look much better and smoother, also would eliminate the need for entering animation for tabs.

// example pseudo code
// State
let currentWorkspace = 0;
let transitioning = false;
let scrollPos = 0; // Scroll progress (-1 to 1)

// Scroll event (hypothetical)
onScroll(progress => { 
  scrollPos = progress;
  updateWorkspaceTransforms(currentWorkspace, progress); // Non-linear visual update
});

onScrollEnd(() => {
  if (Math.abs(scrollPos) > 0.5) {
    goToWorkspace(Math.sign(scrollPos));
  } else {
    animateTo(currentWorkspace); // Snap back
  }
  scrollPos = 0;
});


// Switching
function goToWorkspace(direction) {
  if (transitioning) return;
  transitioning = true;
  const nextWorkspace = currentWorkspace + direction; //... bounds checking
  animateTo(nextWorkspace, () => {
    currentWorkspace = nextWorkspace;
    transitioning = false;
  });
}

// Animation (hypothetical functions)
function updateWorkspaceTransforms(current, progress) {
  // ... apply non-linear transforms based on progress, to current and next ...
}

function animateTo(targetWorkspace, onComplete = () => {}) {
  // ... animate workspaces to target positions (with easing if needed) ...
  onComplete(); // Callback when animation finished.
}

[kristijanribaric]

That would require significant changes to Firefox source code where you wouldn't just create a tab in a tab container, you would have a different tab container depending on a workspace... All in all it's not that trivial and it would require major refactoring for a small gain