WIP: use viewport to allow sizes of scroll to extend further than renderable screen

src/zterm.zig

@@ -1,5 +1,9 @@
+// private imports
 const container = @import("container.zig");
+const color = @import("color.zig");
+const size = @import("size.zig");
 
+// public exports
 pub const App = @import("app.zig").App;
 pub const Renderer = @import("render.zig");
 
@@ -10,18 +14,19 @@ pub const Scroll = container.Scroll;
 pub const Layout = container.Layout;
 
 pub const Cell = @import("cell.zig");
-pub const Color = @import("color.zig").Color;
+pub const Color = color.Color;
 pub const Key = @import("key.zig");
-pub const Size = @import("size.zig");
+pub const Size = size.Size;
 pub const Style = @import("style.zig");
 
 test {
     _ = @import("terminal.zig");
     _ = @import("queue.zig");
 
+    _ = color;
+    _ = size;
+
     _ = Cell;
-    _ = Color;
     _ = Key;
-    _ = Size;
     _ = Style;
 }