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

src/cell.zig

@@ -4,6 +4,7 @@ const Style = @import("style.zig");
 pub const Cell = @This();
 
 style: Style = .{ .attributes = &.{} },
+// TODO: embrace `zg` dependency more due to utf-8 encoding
 cp: u21 = ' ',
 
 pub fn eql(this: Cell, other: Cell) bool {