Split UI code into ly-ui library

Signed-off-by: AnErrupTion <anerruption@disroot.org>

src/animations/Cascade.zig

@@ -1,9 +1,10 @@
 const std = @import("std");
 const math = std.math;
 
-const Cell = @import("../tui/Cell.zig");
-const TerminalBuffer = @import("../tui/TerminalBuffer.zig");
-const Widget = @import("../tui/Widget.zig");
+const ly_ui = @import("ly-ui");
+const Cell = ly_ui.Cell;
+const TerminalBuffer = ly_ui.TerminalBuffer;
+const Widget = ly_ui.Widget;
 
 const Cascade = @This();