add(sizing): grow configuration

Currently the 'grid' and 'mixed' examples are not working yet.

src/element.zig

@@ -94,8 +94,8 @@ pub fn Scrollable(Event: type) type {
             this.size = size;
 
             // TODO scrollbar space - depending on configuration and only if necessary?
-            this.container_size = Point.max(size, this.container.fit_resize());
-            this.container.resize(.{}, this.container_size);
+            this.container.resize(.{}, this.size);
+            this.container_size = this.container.size;
         }
 
         fn handle(ctx: *anyopaque, event: Event) !void {
@@ -206,7 +206,9 @@ test "scrollable vertical" {
             .direction = .vertical,
             .padding = .all(1),
         },
-        .size = .{ .y = size.y + 15 },
+        .size = .{
+            .dim = .{ .y = size.y + 15 },
+        },
     }, .{});
     try box.append(try .init(allocator, .{
         .rectangle = .{ .fill = .grey },
@@ -281,7 +283,9 @@ test "scrollable horizontal" {
             .direction = .horizontal,
             .padding = .all(1),
         },
-        .size = .{ .x = size.x + 15 },
+        .size = .{
+            .dim = .{ .x = size.x + 15 },
+        },
     }, .{});
     try box.append(try .init(allocator, .{
         .rectangle = .{ .fill = .grey },