This commit makes the mode keys transparent in the LOWER layer instead
of disabled.
Before this commit, the following sequence of key presses `LGUI+LOWER+l`
would translate into `Cmd+right` in macOS and, therefore, move the
cursor to the end of line.
But, pressing `LOWER+LGUI+l` would completely ignore the `LGUI` and,
therefore, move the cursor one letter to the right.
With this change, pressing `LOWER+LGUI+l` produces the same result as
`LGUI+LOWER+l`.
This is also true for multiple other combinations, like
`RALT+SHIFT+LOWER+l`, `LOWER+RALT+SHIFT+l`, `SHIFT+LOWER+RALT+l`, etc.
Co-authored-by: Gaston Jorquera <gjorquera@gmail.com>
