Split UI code into ly-ui library

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

ly-ui/src/Cell.zig

@@ -0,0 +1,21 @@
+const TerminalBuffer = @import("TerminalBuffer.zig");
+
+const Cell = @This();
+
+ch: u32,
+fg: u32,
+bg: u32,
+
+pub fn init(ch: u32, fg: u32, bg: u32) Cell {
+    return .{
+        .ch = ch,
+        .fg = fg,
+        .bg = bg,
+    };
+}
+
+pub fn put(self: Cell, x: usize, y: usize) void {
+    if (self.ch == 0) return;
+
+    TerminalBuffer.setCell(x, y, self);
+}