Mac OS modifier layout, plus various tweaks to the standard Tada68 layout.
Uses Grave/Esc on the Esc key so that Cmd+Esc works to cycle through application windows as if the Grave/Tilde key was in the usual place, and sets the GRAVE_ESC_ALT_OVERRIDE flag so that Cmd-Opt-Esc still opens the Force Quit menu.
Blanks on the switches above the Right Arrow and in between the Left Arrow and Fn keys, to give the arrow cluster a bit more separation and make it easier to find by feel.