Add option adjust_baseline to adjust the baseline position on macOS

kitty/state.h

@@ -42,6 +42,7 @@ typedef struct {
     WindowTitleIn macos_show_window_title_in;
     int adjust_line_height_px, adjust_column_width_px;
     float adjust_line_height_frac, adjust_column_width_frac;
+    int adjust_baseline;
     float background_opacity, dim_opacity;
 
     char* background_image;