Add support for VIO_SEL pin to select 1.8V operation

[grunzasr]

Pin 15 is floated (as in your design) for 3.3V IO. Pin 15 grounded is for 1.8V IO. Revision 3 of the datasheet has this in Table 9: MAX-M10S pin assignment on page 9.

If you add two holes for a 2-pin 0.1” jumper to be installed (and a way to disconnect the battery) then the module could be used at 1.8V easily. Just a suggestion in case you ever update the artwork or build a new batch of boards.