feat(terminal/osc12): define cursor color through style of cell that describes the cursor position

The `.default` color will reset the cursor color to the terminal's default color

src/render.zig

@@ -104,6 +104,7 @@ pub const Buffered = struct {
                         .x = @truncate(col),
                         .y = @truncate(row),
                     };
+                    try cvs.style.set_cursor_color(&writer);
                 }
 
                 if (cs.eql(cvs)) continue;