mod(mouse): fix input.Mouse.in method

Pass through mouse events where they actually match the corresponding
`Container`. Adopt mouse event accordingly in `Scrollable` `Element`
trait when passing through the mouse event to the scrollable
`Container`.

src/container.zig

@@ -387,6 +387,10 @@ pub fn Container(comptime Event: type) type {
                         try element.handle(.{ .resize = element_size });
                     }
                 },
+                .mouse => |mouse| if (mouse.in(this.size)) {
+                    try this.element.handle(event);
+                    for (this.elements.items) |*element| try element.handle(event);
+                },
                 else => {
                     try this.element.handle(event);
                     for (this.elements.items) |*element| try element.handle(event);