Start pulling out IO thread and IO implementation

src/termio/Options.zig

@@ -0,0 +1,13 @@
+//! The options that are used to configure a terminal IO implementation.
+
+const renderer = @import("../renderer.zig");
+const Config = @import("../config.zig").Config;
+
+/// The size of the terminal grid.
+grid_size: renderer.GridSize,
+
+/// The size of the viewport in pixels.
+screen_size: renderer.ScreenSize,
+
+/// The app configuration.
+config: *const Config,